Exerts from my essay comparing holistic and chemical modalities of medicine. Please contact me to read the whole essay or to get more info on references.
The bark and leaves of willow species contain salicin, the natural precursor to salicylic acid found in Aspirin type Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) (Foster and Hobbs 2002). In addition to Salicaceae, salicin is found in the Rosaceae genera in Filipendula ulmaria (Meadowsweet), and the Caprifoliaceae genera in Viburnum prunifolium (Black Haw) (Hoffmann 2003).
Salicin precursors are transformed in the stomach and small intestine to create salicin. Salicin can be absorbed in the small intestine, however, it is more commonly absorbed in the distal end of the ileum or in the large intestine. In the large intestine, bacterial flora convert salicin, a glycoside, to salicylic alcohol, an aglycone (the non-sugar component of a glycoside). The salicylic alcohol is then absorbed and converted to salicylic acid, the active form, by oxidization in the blood, liver, and other tissues. (Bone and Mills 2000).
In the 19th century, scientists studied the anti-pyretic and anti-inflammatory actions of Salix alba (White Willow) bark. They experimented in attempts to extract salicin from the bark. The extraction techniques were relatively crude, and they were only able to isolate salicylic acid rather than salicin. Salicylic acid also displays analgesic and anti-platelet actions. Recall that salicylic acid is naturally formed in the large intestine; in the stomach, however, it acts as an irritant (Bone and Mills 2000).
Salicylic acid is commonly ingested in the form, Acetylsalicylic acid (ASA), or Aspirin type NSAIDs. This synthetic form displays a stronger antiplatelet action because of the addition of the acetyl group (Bone and Mills 2000). The anti-platelet action inhibits clot formation in the blood, making it useful in cases of high blood pressure because reduced viscosity of the blood reduces the total peripheral resistance in the blood vessels. However, anti-platelet medicines can also lead to serious side effects such as ulceration of the gastrointestinal tract (Medicine net 2010).
Willow bark is still commonly used in modern herbal medicine, termed phytotherapy. In contrast to ASA, willow bark is not known to have any dangerous side effects or interactions with other medications. The anti-platelet activity displayed by ASA is not seen in the use of plant tissue containing salicin as they are chemically different (Hoffmann 2003). The absence of the acetyl group and the avoidance of salicylic acid contacting the stomach, make Willow bark a safer medication than ASA. In addition to salicin, willow species contain tannins, and therefore offer an astringent property making them useful for diarrhea and throat inflammations (Foster and Hobbs 2002). The comparison of willow and ASA displays the importance of pharmacokinetics when considering the difference between administering chemical derivatives versus whole plant tissues.
As humans and plants interact, each species reacts to others within the ecosystem, resulting in a pattern or energetic change. Plants that have co-evolved with humans are similar energetically as they have been exposed to the same elements or ecological patterns, such as seasonal variations. The co-evolution of human and plant species enables synergistic reactions at both microscopic and macroscopic levels. Holistic care promotes integrated healing by employing whole plant tissues with respect for the adaptive evolutionary form of plant medicines.
Interestingly, the ecosystem provides multiple plant tissues that are useful in combination. The Thompson band of BC used willow branches to splint broken bones; meanwhile they boiled bark to make a poultice and rubbed branches on compound fractures (Turner 1990), presumably to make use of the plants anti-inflammatory and analgesic properties. The long term observation of willow within its natural environment enables humans to benefit from a variety of properties, its salicin, tannins, fibres, and other microscopic and macroscopic materials which have co-evolved with us.
Remember, if you are taking ASA to thin your blood for cardiovascular concerns, Willow is not a suitable alternative. If, however, you are taking ASA for pain, Willow and other salicin containing plants offer a holistic option!