Newsbreaks in herb research
A compound made from the horse chestnut tree may be a more potent skin protectant than vitamin E, according to recent research in Italy.
In laboratory tests, proanthocyanidin A2 (PA2), a derivative of the fruits and inner bark of the horse chestnut tree (Aesculus hippocastanum), showed an intriguing ability to soothe the skin. PA2 scavenged cell-damaging free radicals ten times as well as vitamin E, a potent antioxidant. It was also thirty-one times as effective as vitamin E in inhibiting lipid (fat) peroxidation, which causes scaly skin. PA2 was found to preserve the top layer of skin by protecting ubiquinol, glutathione, and ascorbic acid, the skin’s own free-radical scavengers. It also preserved the skin’s key protective components, such as catalase and superoxide dismutase, and elasticity compounds such as elastin and collagen.
The researchers expect PA2 to be used in suntan lotions and lipsticks to protect skin from accelerated aging caused by sun exposure and to maintain the skin’s natural resilience and elasticity.
Horse chestnut should not be confused with the European chestnut (Castanea sativa) or the American chestnut (C. dentata), sources of the familiar roasting chestnuts. —Kenneth Jones
In the search for nonsynthetic remedies for diabetes, preliminary studies in India indicate that diabetics can lower cholesterol levels by eating the seeds of fenugreek (Trigonella foenum-graecum).
Diabetics have two to three times the risk of cardiovascular disease as nondiabetics, which has been attributed to diabetics’ tendency to overproduce low-density lipoproteins (LDL) or “bad” cholesterol. Bedouin and Yemenite desert tribes have long used an extract of fenugreek seeds to treat diabetes. Researchers interested in this tradition conducted a pilot study on fenugreek and diabetics in parts of India where fenugreek seeds are commonly eaten as a condiment. This led to a more thorough follow-up study at the S.N. Medical College in Agra. For twenty-four weeks, sixty Type II diabetics, none of whom were taking cholesterol-lowering medication, ate 12.5 g of powdered fenugreek seeds in a soup fifteen minutes before lunch and dinner. Significant changes in cholesterol levels were noted after four weeks, and by the end of the study, total mean cholesterol levels had dropped by 14 percent. Levels of triglycerides (which at high levels may increase the risk of heart disease) and LDL and very low-density lipoproteins (VLDL) each dropped by 15 percent. High-density lipoprotein, or “good” cholesterol, increased by 10 percent. In patients who initially had the highest levels of total cholesterol, triglyceride levels decreased as much as 17 percent and levels of LDL and VLDL, as much as 23 percent. Side effects were minimal: a few patients experienced mild flatulence and diarrhea.
Fenugreek seeds’ high proportion of soluble gel fiber is believed to be responsible for lowering cholesterol. —Kenneth Jones
With concerns about the safety of diethyltoluamide, the most commonly used insect repellent, Western scientists are looking to the East for new, natural sources of repellents.
Nearly twenty years ago, the Chinese developed a natural repellent known as quwenling from the waste liquids of lemon eucalyptus (Eucalyptus citriodora). They identified the active constituent as the hydrocarbon p-menthane-3,8-diol (PMD).
Recently, researchers at the London School of Hygiene and Tropical Medicine devised a new method of extracting PMD from eucalyptus oil. This led to the development of a new insect repellent called Mosiguard Natural, which contains 50 percent PMD along with other natural insect repellents such as citronella from lemongrass (Cymbopogon citratus) and isopulegol from pennyroyal (Mentha pulegium).
In laboratory tests using mosquitoes, Mosiguard applied to human forearms in liquid, gel, or stick form was compared with a 50 percent citronella oil repellent and Autan repellent stick, which is 20 percent diethyltoluamide. Mosiguard was slightly less effective against mosquitoes than Autan but twice as effective as citronella and for a longer period. In field studies, Mosiguard lasted as long and was as effective as diethyltoluamide. Against the Scottish biting midge, which in warm climates discourages tourism and work in rural areas, initial tests showed 100 percent protection for six hours after Mosiguard had dried.
Against stable flies, which have an extremely painful bite, an application of 0.5 ml of Mosiguard provided 94 percent protection for five hours. Against ticks, a single application of Mosiguard spray reduced the mean number of ticks that attached to the ears of live rabbits by about 79 percent and reduced the number that fed on the rabbits’ ears by about 78 percent. These results suggest that Mosiguard could protect against Lyme disease, which is carried by ticks. —Kenneth Jones
European pennyroyal (Mentha pulegium) and American pennyroyal (Hedeoma pulegioides) have been used traditionally as teas to treat illnesses such as flu and upset stomach, but misuse of these herbs continues to result in poisoning and even death.
Since classical antiquity, pennyroyal oil has been known to induce abortion. Pulegone, a compound that constitutes 80 to 94 percent of the oil, is highly irritating to the uterus. It is also highly toxic. Ingesting as little as two tablespoons of the oil has caused death; lesser amounts can cause gastrointestinal upset, central nervous system disturbances, and kidney and liver damage.
Four cases of pennyroyal poisoning from the 1990s demonstrate the dangers of using the essential oil or a strong extract of pennyroyal in attempts to induce abortion. In one case, ingestion of pennyroyal essential oil resulted in severe brain damage, liver and kidney failure, and death. The other three cases of poisoning fortunately did not produce lasting effects. Twelve additional cases of pennyroyal poisoning, including four deaths, have also been reported.
Clearly, pennyroyal oil and strong extracts should be avoided without first consulting a health-care professional. —Steven Foster
One of the best-known uses of ginkgo leaf extracts (from the ginkgo tree, Ginkgo biloba) is to enhance short-term memory. More than 300 scientific studies on the use of ginkgo leaf extracts have now led researchers to speculate that they may be of use in relieving mild to moderate symptoms associated with Alzheimer’s disease.
A recent randomized, double-blind, placebo-controlled multicenter study measured the effect of a ginkgo leaf extract standardized for flavonoid and ginkgolide content on 216 outpatients with presenile and senile dementia associated with Alzheimer’s disease. Three established psychiatric evaluation criteria were used to assess their responses.
After twenty-four weeks, information was available on 156 patients: 79 in the treatment group and 77 in the placebo group. Twenty-eight percent of those in the treatment group responded positively to the ginkgo leaf extract compared with 10 percent in the placebo group. Five patients in the treatment group reported minor side effects such as rashes, gastrointestinal complaints, and headache.
This study provides further evidence that supports the use of ginkgo leaf extracts for Alzheimer’s patients in early stages of dementia. In Germany, the extract is approved for this purpose. —Steven Foster
Texas and Nigerian researchers studying the antidiabetic activity of extracts of three species of prickly pear (Opuntia ficus-indica, O. lindheimeri, and O. robusta) in laboratory animals found that the extracts were most effective when administered intravenously. Only O. lindheimeri extract lowered blood sugar when given orally. They also found that a crude extract of the cacti initially raised blood sugar levels briefly before lowering them. The active constituents, which have not yet been identified, apparently occur only in certain species.
Studies of the antidiabetic activity of prickly pears began in the 1920s, but interest was renewed in 1988 when Mexican researchers reported that a preparation made from the pads (flattened stem sections) of O. ficus-indica lowered blood glucose and insulin levels in patients with Type II (noninsulin-dependent) diabetes. They theorized that the preparation may improve the effectiveness of available insulin, stimulating glucose to move from the bloodstream to body cells.
The genus Opuntia includes more than 200 species widely distributed throughout North, Central, and South America. They are found in greatest variety in the southwestern United States and Mexico. Major types, in addition to the flat-stemmed prickly pears, include the cylindrical-stemmed chollas. —Steven Foster
Japanese researchers investigating twelve medicinal plants traditionally used to treat liver disease recently found that woolflower (Celosia argentea) showed exceptional ability to protect the liver against exposure to harmful chemicals. They identified the polysaccharide celosian as the main constituent responsible for protection.
Other polysaccharides have been associated with stimulating the immune system; inhibiting nausea and vomiting; and reducing inflammation, blood-sugar levels, and the incidence of ulcers. This is the first time, however, that liver protection has been attributed to a polysaccharide. Additional pharmacological studies are now under way to determine how it works.
C. argentea is a weedy, silver-flowered member of the amaranth family native to the Tropics. The variety C. a. var. cristata is the colorful, easy-to-grow garden annual that’s often called cockscomb. —Steven Foster
(1) Facino, R. M., et al. “Proanthocyanidin A2: A New Polyphenol”. Cosmetics and Toiletries 1996, 111:49–50, 53–58.
(2) Chandler, R. F. “Horse Chestnut”. Canadian Pharmaceutical Journal 1993, 126:297–300, 306.
(3) Sharma, R. D., et al. “Hypolipidaemic Effect of Fenugreek Seeds: A Chronic Study in Noninsulin-Dependent Diabetic Patients”. Phytotherapy Research 1996, 10:332–334.
(4) Mishikinsky, J. S., et al. “Hypoglycaemic Effect of Trigonella foenum graecum and Lupinus termis (Leguminosae) Seeds and Their Major Alkaloids in Alloxan-Diabetic and Normal Rats”. Archives Internationales de Pharmacodynamie et de Thérapie 1974, 210:27–37.
(5) Trigg, J. K., and N. Hill. “Laboratory Evaluation of a Eucalyptus-Based Repellent against Four Biting Arthropods”. Phytotherapy Research 1996, 10:313–316.
(6) Anderson, I. B., et al. “Pennyroyal Toxicity: Measurement of Toxic Metabolite Levels in Two Cases and Review of the Literature”. Annals of Internal Medicine 1996, 124:726–734.
(7) Kanowski, S., et al. “Proof of Efficacy of the Ginkgo biloba Special Extract EGb 761 in Outpatients Suffering from Mild to Moderate Primary Degenerative Dementia of the Alzheimer Type or Multi-infarct Dementia”. Pharmacopsychiatry, 1996. 29:47–56.
(8) Mofolorunso, A., et al. “Hypoglycaemic Effects of Opuntia ficus-indica Mill., Opuntia lindheimeri Englm. and Opuntia robusta Wendl. in Streptozotocin-Induced Diabetic Rats”. Phytotherapy Research 1996, 10:379–382.
(9) Hase, K., et al. “Hepatoprotective Effects of Traditional Medicines. Isolation of the Active Constituent from Seeds of Celosia argentea”. Phytotherapy Research 1996, 10:387–392.
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