Sunflower Power & Health

October 10, 2016

WITH PERHAPS 25 MILLION ha (62 million acres) of sunflowers grown for seed oil worldwide, sunflower diseases and pests and their remedies have a global impact. “Sunflower oil can be used as an alternative or additive to diesel fuel to create biodiesel, a clean-burning alternative fuel produced from a renewable resource,” wrote G.J. Seiler, one of many worldwide contributing authors to the Compendium of Sunflower Diseases and Pests, a book produced by the American Phytopathological Society (APS), a scientific group whose essence includes plant doctoring, discerning what makes for healthy versus diseased plants. “Use of the product may decrease farmers’ dependence on petroleum fuels by substituting ‘farm-grown’ fuel for use in diesel engines. For use in diesel engines, sunflower oil requires more extensive purification, including removal of waxes and gums. Minor engine modifications, such as improved fuel filters, are also necessary to burn any vegetable oil. Since the energy content of sunflower oil is less than that of diesel fuel, consumption is greater and power output is less.” However, the high-protein residues leftover from sunflower oil extraction have the right amino acid balance to mix with soybean meal to grow healthy chickens and livestock, a virtuous ecological cycling of sunflower plants.

Indeed, in Argentina’s southern Pampas, if you get the planting times right, sunflower and soybean are compatible as intercrops. Working in agriculture, I observed sunflower border rows or perimeters around conventional crop fields attracting pollinators and natural enemies providing biological control of pests. However, sunflowers are so attractive to beneficial insects that they do not want to leave. Thus, sunflower stalks need vigorous shaking to get green lacewings and natural enemies of aphids and other pests to take flight into adjacent crops needing protection. At the moment, fields of GMO canola producing high quality cooking oil are displacing sunflower fields in many areas. But the APS sunflower Compendium awakened my love for sunflowers, as even the diseases afflicting the plants have a certain beauty under the microscope. So, I can see the APS sunflower Compendium serving as an outstanding library reference for biology teachers and students looking for projects in sunflower-growing areas.

R.M. Harveson opens the APS sunflower Compendium with a brilliantly concise narrative chronicling the journey of sunflower seeds from their native North America to Russia, where innovative plant breeders painstakingly created the first modern sunflower seeds high in oils, providing the platform for today’s worldwide sunflower industry. The Mennonites, an anti-violence religious group migrating from Germany (Prussia) and a war-plagued Europe to Russia in the 1780s for free farm land promised by Catharine the Great, pioneered commercial sunflower oilseed farming in a harsh landscape long thought unsuitable for even subsistence farming. Their descendants were lured to Saskatchewan and Manitoba, Canada to create North America’s sunflower industry. During World War II, when “securing the fields of Ukraine was a major objective of Adolf Hitler’s war on Russia,” sunflower oil was a superior antifreeze, lubricating World War II weapons that froze with conventional gun oils. Joe Pappalardo’s excellent and entertaining book, Sunflowers: The Secret History: The Unauthorized Biography of the World’s Most Beloved Weed (Overlook Press) adds color and specifics, and is cited in Harveson’s “Selected References” in the APS Compendium.

Personally, I love the feel on my head and hair of a shampoo blending organic sunflower oil, citrus oils and herbs; and organic sunflower seeds at breakfast supply trace minerals like zinc, which is often deficient in produce grown in local California soils. Sunflower sap, which occasionally has been used medicinally, contains terpenoid compounds that show potential as alternative botanical pesticides. As ingredients in traditional medicines, wild sunflowers have been used for everything from wound healing and rattlesnake bites to combating infection and pain relief. Modern medical uses include topical oil formulations with sunflower oil to improve skin health, fight fungal infections, relieve inflammation and itchy, dry skin, and in dentistry to improve the gums.

Seed hulls of certain sunflower varieties are traditional sources of yellow, ruby red, purple, and black dyes or colorants (e.g. anthocyanins) useful in body painting, cosmetics, foods and textiles. Indeed, some plant breeders are working on a sunflower seed that would be high in oil and have a ruby red husk or hull that could be extracted to replace commercial synthetic red food dyes. Other researchers see the hulls as useful absorbents for wastewater reclamation. But by far, sunflower seed oils (e.g. NuSun for cooking) are the main sunflower item of commerce, and even trade on the commodities futures markets. Sunflowers seeds like Mammoth Russian for eating and snacking or adding to birdseed blends are important crops, but minor compared to the large acreages of sunflower oilseeds grown worldwide.

For various reasons, sunflowers have not become commercialized as a biotech GMO (Genetically Modified Organism) crop, which makes life easier for organic growers. Though perhaps better known from Van Gogh canvases, sunflowers were experimental subjects on the USA’s Apollo space missions. And “sunflowers have been successfully used as vehicles for the phyto-remediation of soil contaminated with heavy metals and radioactive materials (e.g. following the Chernobyl disaster),” wrote Harveson. In March 2011 after the Great East Japan Earthquake and Fukushima Daiichi Nuclear Power Plant accident, sunflowers and sunchokes were among the “alternative technology” plantings to concentrate and remove from soils radioactive cesium, which emits gamma rays and has a 30-year half life.

Sunchokes or Jerusalem artichokes, perennial sunflowers grown for edible tubers high in inulins, are sometimes recommended for diabetes and cardiovascular diseases, being associated with lowering blood sugar and cholesterol. Indeed, Jerusalem artichoke chips have been tested as a snack food alternative to potato chips for diabetics, being almost devoid of starch and fats. Several dozen other sunflower species are known, including one that is 92% pure natural rubber. Most likely sunchokes and other sunflower species including backyard ornamentals are subject to pests and diseases similar to those described in the APS Compendium.

To prevent pests and diseases, as a kind of insurance, perhaps 95% of commercial sunflower seeds are coated with neonicotinoid pesticides (e.g. thiamethoxam, clothianidin) at planting time, according to Michael Bredeson of South Dakota State University in Brookings at the 2015 joint meeting in Minneapolis of the Entomological Society of America (ESA), the American Society of Agronomy, the Crop Science Society of America, and the Soil Science Society of America. Bredeson studied 11 commercial sunflower fields, and found that “the seed treatment failed to improve yield or decrease herbivores.” In other words, quite apart from whatever effects on honey bees and beneficial organisms higher in the food chain, the neonicotinoid seed treatments are mostly a waste of resources and money. Though perhaps they do buy peace of mind for commercial sunflower growers, much like any insurance policy.

But the peace of mind bought by unnecessary early-season pesticide seed treatments may bring ecological food chain effects that cost sunflower growers more money and crop loss later in the season. The neonicotinoid pesticides may enter the food chain via plant nectar, plant tissues and predator consumption of tainted prey. Indeed, Pablo Gontijo and colleagues (2015) reported that sunflower seeds treated with thiamethoxam poisoned minute pirate bugs (Orius insidiosus), which are major predators of aphids, caterpillars, spider mites and other pests. Part of the problem is that the beneficial bugs, besides eating pests, also suck moisture directly from plants and thereby become poisoned by systemic pesticides used as sunflower seed treatments.

Likely the poisoned pirate bugs are only the tip of the proverbial iceberg. At the 2015 ESA meeting, Sirilak Lankaew from RYFCRC in Rayong, Thailand reported that cassava cuttings treated preventively with thiamethoxam provided 1-2 months cassava mealybug protection at the cost of food chain effects on beneficial insects via poisoned cassava nectar. Specifically the wasp Anagyrus lopezi, a cassava mealybug natural enemy, feed on the poisoned cassava nectar and “experience acute mortality for up to 21 days after treatment, and have significantly reduced lifespan for at least 42 days after treatment.” With 8 million farming households in Thailand growing cassava and 70% of Thailand’s small-scale farmers using neonicotinoid pesticides, there is a need for alternative technologies “fully compatible with (naturally-occurring and cost-free) biological control.” In sunflower, something like the APS Compendium to identify the potential problems is a good first step towards minimizing unnecessary pesticide treatments and developing alternative technologies.

One approach to developing sunflower soils that are disease-free and avoiding seed treatments is the opposite of crop rotation. Namely growing the crop repeatedly in the same soil so that disease organisms build up and then are destroyed by natural biological agents. It is like the predator and prey cycle, where pests buildup to high levels and even cause some damage before being opportunistically exploited and knocked down by their natural enemies. This approach, known as building a disease suppressive soil, can take a few years; and is perhaps best suited to patient organic growers with the wherewithal to weather those tough early years, and possessed of a confidence, hope or faith that the natural cycles will eventually play out. Likely the Mennonites whose experiences Joe Pappalardo recounts in his book took this route in turning the barren Ukraine, Russian and Canadian lands into productive agricultural fields in the era predating intensive chemical agriculture.

Another interesting alternative technology with ancient roots is interplanting, the idea of mixing different crops in the same fields. In Pakistan, sunflowers are being considered as a healthful alternative for local cooking oil shortages via interplanting sunflowers with the staple mungbean crop. In Florida, sunflower strips have been proven to attract honey bees and a variety of predators and parasitoids supplying natural biological pest control to adjacent organic vegetables. In China, parts of Asia and Africa, and even the Americas, sunflowers are viewed as an alternative technology to reduce herbicide use. Sunflowers provide natural weed control via shading the ground and natural herbicidal compounds (allelochemicals) toxic to some of the world’s worst weeds, such as dodder and barnyard grass. Multiple benefits if you can get rid of a weed patch, produce beneficial insects and pollinators, and harvest some seeds at the same time.

The health benefits of sunflowers will likely be a key driver for this crop in the future, though medicinal sunflower benefits are far from the cutting edge of agriculture and medical research in the genomic era. Broader medical applications may involve anti-inflammatory and cardiovascular benefits, bone health, detoxification, skin protection (e.g. from light & anti-aging) and anti-cancer effects. Applied to the skin, sunflower oil formulations may reduce bacterial and fungal infections, and are touted by some for premature newborns. In Cuba a product called Oleozon, sunflower oil treated with ozone gas, was registered in 1999 to treat fungal skin diseases (tinea pedis); and can stop bacteria and viruses resistant to multiple drugs.

Interestingly, researchers in Iran writing in the Journal of Food Science and Technology like the idea of infusing highly unsaturated oils like sunflower seed oil with raspberry or related Rubus species (e.g. blackberries) as a GRAS (Generally Recognized As Safe) alternative to preservatives like BHA and BHT. Rubus leaves add other medicinal properties to sunflower oil, “including as astringent, hypoglycemic, anti-diarrhea, anti-inflammatory agents for mucous membrane of oral cavity (mouth) and throat.” Many other oils and herbs may have medicinal value when combined with high linoleic acid sunflower oil. Time will tell.

The whole idea of plant medicines may yet return to modern medical practices for a variety of reasons. “Extended life expectancy is accompanied with an increase in age-related pathologies that include cardiovascular and neurological diseases, obesity, and cancer, conditions that are inflicting an immense pressure on health care costs and quality of life,” write researchers Andrea Doseff and Erich Grotewold at The Ohio State University and Arti Parihar in Ujjain, India, in the book, Pigments in Fruits and Vegetables (Springer, 2015). “Thus, there has been an increased interest in recognizing and understanding the mechanisms of action of active nutritional compounds with health benefits, or nutraceuticals, for the prevention and treatment of various diseases.”

The researchers in India and Ohio note that over 8,000 flavonoid chemicals beyond vitamins have been identified, including a range of anthocyanins like those in sunflowers, “which are responsible for providing colors to fruits and vegetables, and have dietary value as color additives with potential health benefits.” Over 10,000 tons per year of anthocyanins from black grapes alone are consumed every year, and this whole general category of plant pigment compounds has “uses in the prevention and treatment of inflammatory diseases including cardiovascular diseases, obesity, and cancers.” Who knows what concentrated research into sunflowers would reveal?

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Pigments of the Imagination: Cochineal’s Renaissance

June 22, 2016

SAP-SUCKING SCALE INSECTS, such as cochineal, kermes and lac, are sometimes sprayed with pesticides as landscape and crop pests, and other times cultivated as beneficial insects. For example, cochineal secals have provided biological weed control in India, Australia and South Africa where imported prickly pear cactus (Opuntia spp.) hedges have escaped and become rangeland weeds. Cochineal scale insects, bred in ancient Mexico to yield 15%-30% color pigment content, have been grown in the Americas for many centuries on prickly pear cactus as a sustainable, biodegradable colorant crop yielding dyes ranging from red, yellow, orange and brown to pink, lavender and purple (depending on mordant, pH, etc.). Intensely red cochineal has a long and famous history in painter’s palettes, tapestry and fabrics, and has been used for centuries to color or stain tissues red or purple for microscope visibility in biology and microbiology labs, medicine and dentistry. Cochineal scale pigments also color selected beverages, foods (on labels as E-120 & carmine) and cosmetics like lipstick, rouge and nail polish. Biochemistry labs like the cochineal red molecule’s ability to bind or bond with proteins, nucleic acids and fats (lipids). Analytic chemists use cochineal “for photometric determination of boron, beryllium, uranium, thorium, and osmium.” At the cutting edge frontier of science, cochineal pigments are being adapted to “molecular information processing” and computing. The red pigment’s “strong photosensitization and photocurrent switching effects” are being designed into next generation optoelectronic (i.e. light, photon) devices like semiconductors, fuel cells, sensors and photovoltaic solar energy systems.

“In Latin-the indispensable language of Renaissance medical professionals—the word pigmentum signified both a pigment and a drug,” writes Amy Butler Greenfield on page 83 of the paperback edition of her meticulously researched book, A Perfect Red, which follows the parallel rise and fall of the Spanish Empire and the secretive cochineal red export trade. “Artists who made their own paints were often advised to procure cochineal from their local “Drugist” or pharmacy, advice that highlights the fact that Europeans also used cochineal as a medicine,” a practice “at least partly borrowed from ancient Mexico,” where cochineal was used to clean teeth and also dissolved in vinegar and applied as a poultice to cure wounds and strengthen bodily organs. Spain profited more from importing cochineal into Europe than from all its plundered and mined New World gold. When ancient alchemy’s metamorphosis into modern chemistry advanced to synthesizing a less expensive, wider range of brighter dye pigments, the Spanish red dye monopoly was obsoleted and the financial collapse of the steadily weakening empire allowed for a global power shift; the USA, fresh from coast to coast expansion and hot for global colonial-style conquests, easily knocked off the remnant hollow shell of the Spanish Armada in the Caribbean and Philippines in 1898.

Let’s start with cochineal and scale insects as pests, and organic control alternatives, as that is how most people encounter and view scale insects. Parasitoid wasps, lady beetles, birds and many other natural enemies provide biological control of scale insects, but not always enough at the right time. Highly refined petroleum oils, vegetable oils and high-pressure water sprays (with or without soap or surfactants) are among the often used remedies. High pressure water sprays, from a nozzle or heavy overhead rainfall, wash off or injure cochineal scales; and this remedy is sometimes used post-harvest by packing houses to clean fruit prior to shipping. Laboratory studies indicate that epazote (Chenopodium ambrosioides), mint (Mentha spp.) and marigold (Tagetes spp.) extracts applied with emulsifiers are potential organic or environmentally friendly synthetic pesticide alternatives.

At the Entomological Society of America (ESA) annual meeting in Minneapolis I talked with Colorado State University extension entomologist Whitney Cranshaw, whose special spiked shoes for killing white grub beetle larvae beneath the soil surface while walking golf course turf and lawns achieved notoriety in Smithsonian magazine many moons ago. This time he was a lonely entomologist, as out of hundreds of passersby no one was stopping at the poster of graduate student Rachael Sitz reporting on a kermes scale vectoring a bacteria causing drippy blight of red oaks in Colorado. Cranshaw was ecstatic having a customer, and figured I was studying the poster display because the kermes scale was also found in California locales such as San Jose, Mammoth Lakes and Monticello Dam on blue oaks and chinquapin bushes. Actually, I was wondering if this particular kermes scale, which went by the scientific name Allokermes rattani, was related to Old World kermes scales used for centuries by pigment artists in Europe and Asia. According to Cranshaw, workers handling the Colorado kermes scale came away with hands dyed a deep brown. So, perhaps this “pest” scale insect is indeed an untapped resource, similar to cochineal, waiting to be discovered by textile artists, painters and photographers looking for natural organic pigments.

My own interest in these insect pigments is a bit abstract, how to incorporate these pigments into the photographic printing process, inspired in part by viewing Robert Rauschenberg’s vegetable pigment prints with photo images from Indonesia. Cochineal was apparently on occasion used in early color photography printing, dating back to the 1800s and heliochromes, which I surmise are solar prints that also use silver as a light-sensitive pigment. Some modern authors talk of a “green synthesis,” fusing conventional silver nanoparticle photography with cochineal red pigments; but I have not found much on the subject. “Color photography,” U.S. Patent No. 923,019 from 25 May 1909 reads: “To all whom it may concern: Be it known that I, EDGAR CLIFTON, a subject of His Majesty the King of the United Kingdom of Great Britain and Ireland, residing at 3 BeaufortVillas, London Road, Enfield, in the county of Middlesex, England, have invented certain new and useful Improvements in Color Photography…known as the two color process; the three color process; and the four plate process…so that the assemblage gives more or less natural color effects…As the red dye: alizarin (with alumed reliefs), cochineal red (or carmin with ammonia), or magdala red…”

SCALING UP PRODUCTION of pigment scales, versus natural harvest, is often surprisingly difficult. For one thing, about 14,000 individual scale insects are needed to obtain 100 grams of raw cochineal pigment. Far from being dumb savages, ancient Mexico’s New World cochineal growers were superb insect breeders. The best cochineal “breeds” contain 18%-30% pigment by dry weight. Spaniards settling in the New World never mastered the delicate art of cultivating cochineal scale on prickly pear cactus, and instead relied on the indigenous los indios de Mexico, some of whom grew rich on the cochineal trade in what was essentially a free market. Many Spanish colonists found it intolerable that the natives were becoming the richest citizens, and this led to all kinds of frictions and conflicts aimed at turning the natives into poorer, more docile (less uppity) and easier to control colonial subjects. The Spanish were remarkably successful at keeping curious outsiders out of the cochineal production areas for centuries, making the cochineal red dye one of the world’s all-time best kept trade secrets. Most Europeans assumed the grana or granules of cochineal were seeds or plant material, like indigo or madder. On those rare occasions when the secret was revealed, the public refused to believe that cochineal red was literally dried insects. This combination of secrecy and worldwide ignorance allowed the Spanish cochineal monopoly to persist for several centuries and be more lucrative than precious metals.

As any entomology grad student can tell you, the same insect that is an abundant pest can often be impossibly hard to grow when you want it for experiments or as a thesis subject. For one thing, the “insect crop” usually has its own set of pests (called natural enemies), which for cochineal scales includes bacteria, lady beetles, syrphid or hover flies, predatory caterpillars, rodents, reptiles and birds. To prevent “crop failure,” cochineal scales need pampering and protection: 1) from natural enemies; 2) shade to protect from direct sunlight; 3) shelter from heavy rains that wash off and injure the scales. Raising cochineal scales as “farm animals” or “livestock” on prickly pear cactus was often a family enterprise in Old Mexico, an art or skill passed down from generation to generation. The prickly pear cactus itself is still also food, animal fodder and medicine in Mexico. But cochineal grana are no longer treated like money or currency, as it was in Aztec Mexico when cochineal was used in payment of tribute or taxes. In that sense, in contrast to a modern dollar, euro, yen, peso, pound, rupee or digital currency, which cannot be directly used as dyes or medicines, the grana possessed an exquisite versatility and flexibility in ancient times.

CARMINIC ACID, a MEDICINAL CHEMICAL pigment compound extracted from cochineal and first synthesized in 1998, belongs to a class of anti-tumor and antibiotic compounds called anthracycline derivatives, which “are believed to develop their cytotoxic effect by penetrating into the tumor cell nucleus and interacting there with DNA,” write chemists at Gazi University in Ankara, Turkey. Combined with other compounds, cochineal is also active against viruses and other microbes. In Tamil Nadu, India cochineal scale insects collected from cacti are crushed, boiled in water and dried to a powder used against whooping cough and as a sedative. Other traditional uses likely abound.

In nature, cochineal functions as an insect repellent. One theory is that cochineal repels ants, protecting young scale insects before their protective waxy outer covering forms. A carnivorous caterpillar eating the scales incorporates the cochineal dye into its own bodily defenses. A study in the Journal of Polymer Science concluded that cochineal and other natural dyes (madder, walnut, chestnut, fustic, logwood) and mordants (aluminum, chrome, copper, iron, and tin) increased the insect resistance of the wool fabric to attack by black carpet beetles.” Indigo was least effective, and cochineal and madder were most effective except when used with tin and chrome as the mordant or binding agent. I only remember one ESA presentation investigating cochineal as a natural insecticide, and that was back in 2004; the idea was that since carminic acid was already approved as safe for food by the FDA, cochineal could be formulated as an organic bait spray to stop fruit flies without losing organic certification. The researcher theorized that cochineal needs sunlight to be activated as an insecticide, and would thus be ideal for organic agriculture. But as far as I know, the idea was never adapted as an agricultural or quarantine practice.

COMBINING COLOR and HEALING is, however, an idea gaining traction. Carminic acid, a brilliant red compound constituting about 10% of cochineal8, “is one of the most light and heat stable of all the colorants and is more stable than many synthetic food colors,” write Khadijah Kashkar and Heba Mansour in the Department of Fashion Design at King Abdul Aziz University, Saudi Arabia. “Besides the color attributes, recently, also has been reported to beneficial to health with potential antibiotic and antitumor properties. At the beginning of the 21st century it is predicted that many colors will be used for both their additional beneficial functions in the body, as well as, coloring effect.” Whether color and healing were also linked in ancient or Aztec times with cochineal is an intriguing question. Perhaps everything old is indeed new again, but who knows what the ancient New World healers or shaman thought when applying bright red or purple cochineal poultices.

PREVENTIVE MEDICINE might be what to call the combination of organic cotton and natural cochineal dyes to block ultraviolet light from skin contact. Ajoy Sarkar of Colorado State University, writing in the journal BMC dermatology: “The ultraviolet radiation (UVR) band consists of three regions: UV-A (320 to 400 nm), UV-B (290 to 320 nm), and UV-C (200 to 290 nm). UV-C is totally absorbed by the atmosphere and does not reach the earth. UV-A causes little visible reaction on the skin but has been shown to decrease the immunological response of skin cells. UV-B is most responsible for the development of skin cancers…Other than drastically reducing exposure to the sun, the most frequently recommended form of UV protection is the use of sunscreens, hats, and proper selection of clothing. Unfortunately, one cannot hold up a textile material to sunlight and determine how susceptible a textile is to UV rays.” Heavy concentrations of synthetic dyes in synthetic fabrics generally provide good UVR protection, but are not as comfortable as cotton fabrics for warm, humid climates. Generally, the darker the color and the thicker the weave or denser the fabric, the better to protect against UVR. Depending upon the weave (e.g. twill vs sateen), Sarkar reported good to excellent UVR protection with natural dyes such as madder, indigo and cochineal.

COCHINEAL’S 21ST CENTURY RENAISSANCE and resurgence includes harnessing cochineal’s ability to capture (harvest) or route light (photons) and electrons in advanced or next generation optoelectronic devices such as semiconductors, light harvesting antennae, sensors, fuel and solar cells, and molecular information and logic gates for computing devices. I was surprised to learn that natural pigments have a long history in advanced electronics: “As early as the birth stage of lasers, coumarin, which is found naturally in high concentration in the tonka bean (Dipteryx odorata), was used in dye lasers” and “coumarin dye is still the basic active medium for many tunable dye laser sources,” writes M. Maaza (2014) of the University of South Africa. “Extracts from Hibiscus sabdariffa, commonly known as Roselle, carminic acid of the cochineal scale and saffron exhibit exceptional nonlinear optical (NLO) properties of a prime importance in optics.”

THE “NEXT GENERATION” SOLAR CELL replacement for today’s silicon-based solar cells will probably be a dye-sensitized solar cell (DSSC) based on titanium dioxide (TiO2), a semiconductor material that is fused with color pigments analogous to those used in conventional color photography (e.g. silver halide emulsions sensitized by dyes). TiO2 and other metal oxides are widely used in medicine, food preservation, cosmetics, sunscreens, paints, inks and a wide range of electronic devices for sensing, imaging, optics, etc. TiO2 is relatively inexpensive, and deemed low toxicity. Interestingly, TiO2 nanoparticles for solar cells can be produced from cultures of bacterial cells, such as the Lactobacillus sp. found in yogurt or curd, which means an even “greener” solar cell fabrication process.

The scientific roots of the modern solar cell go back to French physicist Edmond Becquel’s discovery of the photovoltaic effect in 1839; and prototype solar cells with efficiencies of 1% or less also date back to the 1800s. Though Albert Einstein explained the photovoltaic effect in 1904, the development of lightweight solar energy cells to power spacecraft in the 1950s. But the DSSC or Grätzel cell is a 1990s’ innovation attributed to Mr. O’Regan and Michael Grätzel. “This new device was based on the use of semiconductor films consisting of nanometer-sized TiO2 particles, together with newly developed charge-transfer dyes,” and had “an astonishing efficiency of more than 7%,” write Agnes Mbonyiryivuze et al. (2015) in the journal Physics and Materials Chemistry.

Next generation DSSCs or photovoltaic cells are currently undergoing a major design transition using natural color pigments like those found in cochineal scale insects. DSSCs with efficiencies in the 10% to 15% range can be manufactured with titanium dioxide (TiO2) nanoparticles bonded on a thin film with a light-sensitive dye utilizing a rare and expensive platinum group heavy metal, ruthenium (Ru; named after Russia). Ruthenium’s relatively high cost and environmental and toxicology concerns are a barrier to commercialization that is spurring the search for substitutes; namely cheaper and more environmentally friendly natural pigment. Companies working “to bring DSSC technology ‘from the lab to the fab’” include “Dyesol, G24i, Sony, Sharp, and Toyota, among others,” write Mbonyiryivuze et al. (2015). “Functional cells sensitized with berry juice can be assembled by children within fifteen minutes, the large choice of colors, the option of transparency and mechanical flexibility, and the parallels to natural photosynthesis all contribute to the widespread fascination. In 2013, the drastic improvement in the performance of DSSC has been made by Professor Michael Grätzel and co-workers at the Swiss Federal Institute of Technology (EPFL). They have developed a state solid version of DSSC called perovskite-sensitized solar cells that is fabricated by a sequential deposition leading to the high performance of the DSSC. This deposition raised their efficiency up to a record 15% without sacrificing stability…this will open a new era…even surpass today’s best thin-film photovoltaic devices.”

“PIGMENTS MAKE NATURE COLORFUL and LIKABLE,” writes Chunxian Chen, a researcher at the University of Florida’s Citrus Research and Education Center and the editor of a 277-page book published by Springer in 2015, Pigments in Fruits and Vegetables: Genomics and Dietetics, which places a heavy emphasis on the nutritional and medicinal benefits of colorful natural pigments like those coloring crops of carrots and sweet potatoes orange and radishes and tomatoes red. “Plant pigments usually refer to four major well-known classes: chlorophylls, carotenoids, flavonoids, and betalains…Chlorophylls are the primary green pigments for photosynthesis. The latter three are complementary nongreen pigments with diverse functions…The importance of colors in living organisms cannot be overstated…they are biosynthesized behind the scenes in living organisms and ultimately ingested in daily diet.” Presumably this daily consumption and medicinal benefits makes natural pigments in general logical and sustainable alternatives to expensive heavy metals in “green” electronic, computer and solar energy cell designs.

Agnes Mbonyiryivuze, in her 2014 dissertation titled “Indigenous natural dyes for Gratzel solar cells: sepia melanin,” provides a readable overview of solar energy cells utilizing natural pigments. The list of natural pigments fabricated into solar cells is long, and the sources range from cochineal scale insects, green algae, baker’s yeast, fungi and bacteria to bougainvillea flowers, Chinese medicinal plants (e.g. tea, pomegranate leaves, wormwood, mulberry fruit) and food crops like beets, parsnip, purple cabbage, blackberry and black grapes. The black pigments are of particular interest, including skin melanins providing UV protection and the black powder from cuttlefish (Sepia officinalis) ink sacks. “To maximize the absorption of more photons from the sun light for DSSC,” writes Mbonyiryivuze, “it is better to have a black dye sensitizer having extremely high broadband absorption. It should absorb not only in visible range but also in ultraviolet and near-infrared regions. This challenge can be handled by using natural dyes from other sources such as fauna from which sepia melanin was obtained. Melanins are well-known natural pigments used for the photoprotective role as a skin protector because of their strong UV absorbance and antioxidant properties. Melanin possesses a broad band absorbance in UV and visible range up to infrared.” Sepia melanin “can also conduct electricity and is thus considered a semiconductor material.”

“There are numerous trials of solar cell construction which are based on biomolecules and supramolecular systems, for instance, chlorophylls, porphyrins, phtalocyanines, and other natural or bioinspired dyes,” write researchers in Poland constructing double layer solar cells with cochineal red and gardenia yellow pigments bonded to TiO2 nano-surfaces. “Hybrid materials incorporating biomolecules immobilized on conducting or semiconducting surfaces are unique systems combining collective properties of solids with structural diversity of molecules, which besides photosensitization show other unique electrochemical and catalytical properties.”

According to Mousavi-Kamazani et al. in Material Letters (2015), quantum dots composed of cochineal and copper offer the economically attractive “possibility of single step production of three-layered solar cells.” Clearly, though the distance might be measured in years or decades, we are getting closer to a cochineal and natural pigment renaissance that transcends traditional fabric dyes and artist’s pigments and extends into medicine and the heart of modern computers, lasers and electronic and optical devices of all sorts.