Active Constituents In Medicinal Herbs
Plants produce a bewildering variety of chemical compounds to maintain the vigour to grow, produce seed and resist environmental challenges. Some plants have been shown to contain hundreds of different constituents. Teasing out which ones have direct medicinal activity is a highly complex task, one that lies at the heart of pharmacognosy – literally, the knowledge of plant medicines, and phytochemistry – the study of plant chemistry.
Knowing a little about the active compounds contained in plants helps one to understand how they work in the body. Some of the most important constituents are:
Phenols: Often antiseptic and anti-inflammatory, these are produced by plants to prevent infection. Carnosol, found in Rosemary and Sage, has anti-inflammatory, anti-cancer and nerve protective activity. Thymol, present in Thyme, is strongly antiseptic and antiviral.
Volatile oils: Once extracted from the plant, these constituents are known as essential oils. They can contain 100’s of different compounds and have many uses. Some oils are relaxant and relieve pain e.g. Lavender, others are stimulant and anti-inflammatory e.g. Ginger.
Flavonoids: These have a wide range of actions. Hesperidin and rutin, found in many plants - notably in citrus fruit such as Lemon, act to support a healthy circulation, particularly improving capillary flow.
Tannins: Found at high levels in barks, e.g. Willow bark, and produced by plants to resist insect attack and grazing, tannins are astringent (they tighten up tissue) and have an unpleasant drying taste. Tea (Camellia sinensis) that has been left too long to brew has the typical tannin taste.
Proanthocyanins: Known for the red, purple and blue colour they impart to flowers and fruit, e.g. Hawthorn berry, these constituents support cardio-vascular health and counter inflammation within blood vessels.
Coumarins: Present in many plants, these constituents have variable activity, some are anti-coagulants, some anti-inflammatory, some reduce anxiety, e.g. in Angelica.
Saponins Saponins: form a soapy lather in water. Many have key medicinal activity, in part due to their similarity to the body’s own hormones, such as oestrogen and cortisol. Sarsaparilla contains at least 5 five different steroidal saponins.
Cyanogenic glycosides: In small doses, these constituents, which are based on cyanide, relax respiratory muscles, making them useful in soothing dry, irritable coughs. Elderberry contains low levels of these compounds.
Polysaccharides: Present in all plants, these compounds are found in mucilage and gums, and help the plant to maintain water levels. They are soothing to the skin and mucus membranes. Some polysaccharides support immune function e.g. Echinacea purpurea.
Bitters: Chemically diverse, all bitters have a bitter taste. The taste itself stimulates digestive function, including stomach and intestinal secretions. Hops are well known for their bitter taste.
Alkaloids: These are some of the most powerful plant constituents, morphine from the Opium poppy being a prime example. Capsaicin is another alkaloid, the constituent most responsible for the heat in chilli pepper.
Medicinal plants can also contain appreciable levels of vitamins and minerals.