Astringent herbs as vasoconstrictors in haemorrhoid therapy

Haemorrhoids are cushions of tissue and varicose veins located in and around the rectal area. Treatment includes over-the-counter topical medications, surgery and herbal therapy. Astringency is not a taste but a feeling of dryness or roughness that is sensed by the tongue as a result of increased friction between the tongue and the surfaces inside the mouth. This is thought to be caused by tannin, which reduces lubrication by precipitating salivary proteins.

As part of our ongoing investigation on astringent herbs, some medicinal plant extracts used locally in the treatment of haemorrhoids [Achyranthes aspera Linn. (Amarantheceae), Adansonia digitata L. (Bombacaceae), Dialium guineense Willd (Leguminosae), Harungana madagascariensis, Newbouldia leavis Seem. (Bignoniaceae), Spondias mombin L. (Anacardiaceae)], were subjected to an astringency assay. This was based on the characteristic of astringents to tannins.

Astringency was measured as the amount of tannin precipitated by a standard protein bovine serum albumin (BSA). Extracts were added to a solution of BSA in a buffer that allowed maximum precipitation of the tannin-BSA complexes. The precipitate was collected by centrifugation, dissolved in a basic buffer containing detergent that disrupted the hydrogen bonds holding the protein- tannin complexes together in the precipitate.

The soluble tannin present in the precipitate was measured using ferric chloride. Ferric ion complexes with the tannins and forms a blue chromophore with an absorbance maximum at 510 nm. The blue product was determined photometrically and compared to a standard curve prepared with tannic acid. Astringency was reported as mg/L tannic acid equivalents.

Astringency of extracts was in the order of Spondias (746.86±0.65) > Dialium (471.17±0.65) > Harungana (132.09±0.10) > Newbouldia (96.48±0.08) > Adansonia (82.98±0.43) > Achyranthes (36.03±1.05). It is proposed that these astringent herbs accomplish haemorrhoid activity by plugging up minute leaks and holes in the veins and capillaries thereby promoting vein elasticity and acting as vasoconstrictors in the perianal area.