Herbal Drugs: Chemical | Organic composition
Last modified: Sunday, 31. May 2009 - 3:58 pm
The chemical composition of herbal drugs is highly complex and uncertain, especially when compared with conventional drugs. Herbal drugs contain all the chemicals inherent in the plant. Even when the active ingredient in an herbal product is known (or suspected), it is difficult for manufacturers to standardize how much active ingredient their product contains. The potency of herbal drugs is affected by growing conditions, storage, handling, and the manufacturing process used. For example, one manufacturer might grind plants up and put them into pill form, while another might prepare an extract from the plant. The consumer protection-focused magazine Consumer Reports examined the composition of herbals and found that the potency of products based on the same plant varied as much as 10,000 fold.
Herbal products do not always contain the plant they are supposed to contain. In an apparent case of mistaken identity, the Chinese herbal slimming aid “Fangji” was replaced by “Guang fangji” and distributed in Germany and France. The highly toxic Guang fangji caused several cases of a kidney disease known as fibrosing interstitial nephritis. Producers of herbals have also cut costs by padding their product with related but cheaper plants. Because of the high cost of pure ginseng, some products labeled as ginseng are supplemented with mandrake or snakeroot.
Herbal drugs may contain additives not listed on the label, and these additives are sometimes the source of the “herbal” medicine’s effect. Investigations by Consumer Reports and others have shown herbal products to contain aspirin, caffeine, steroids, non-steroidal anti-inflammatory drugs, antibiotics, sedatives, and even narcotics.
Finally, herbal products imported from China may be contaminated with pesticides or with heavy metals added during the manufacturing process. Contaminated Chinese herbals have led to cases of arsenic, lead, mercury, thallium, and cadmium poisoning. Similarly, investigations of traditional Indian Ayurvedic remedies have shown them to sometimes contain dangerous levels of lead, zinc, mercury, arsenic, aluminum, and tin.
Flavonoids: an active ingredient in many herbals
Many medicinal plants contain chemical compounds called flavonoids. Some evidence suggests that flavonoids, also called bioflavonoids, can have beneficial effects on the body. Flavonoids may be able to help ward off bacteria and viruses and reduce inflammation. They may also be antioxidants, which are molecules that clear the body of harmful chemicals called oxygen free radicals. (Oxygen free radicals are highly reactive molecules that damage cells and have been associated with diseases such as cancer, diabetes, and cardiovascular disease.)
Flavonoids concentrate in the seeds, bark, flowers, or fruit of most plants. The herbal remedy green tea (Camellia sinensis), which is used for stomach disorders, contains about 30% flavonoids by weight. Apples and onions, which are listed in the Physicians’ Desk Reference for Herbal Medicines (PDR-HM), also contain high amounts of flavonoids.
Flavonoids are divided into many classes and subclasses, each with a slightly different chemical structure and function. Classes of flavonoids include flavanols, flavanones, catechins, anthocyanins, and isoflavones. Subclasses of flavonoids include genistein, found in soy, and quercetin, found in onions.