Spasmogenic and spasmolytic activities of Agastache mexicana ssp. mexicana and A. mexicana ssp. xolocotziana methanolic extracts on the guinea pig ileum.

ETHNOPHARMACOLOGICAL RELEVANCE: Agastache mexicana has been used in traditional medicine for relief of abdominal pain and treatment of other diseases. Two subspecies have been identified: A. mexicana ssp. mexicana (AMM) and A. mexicana ssp. xolocotziana (AMX) and both are used traditionally without distinction or in combination.

AIM OF THE STUDY: To determine the effect of methanol extracts of A. mexicana ssp. mexicana and A. mexicana ssp. xolocotziana on gut motility and their possible mechanism of action.

MATERIALS AND METHODS: The effect of AMM and AMX methanol extracts were tested on the spontaneous activity in the isolated guinea pig ileum and on tissues pre-contracted with KCl, electrical field stimulation (EFS) or ACh. In addition, the possible mechanism of action of each subspecies on gut motility was analyzed in the presence of hexametonium, indomethacin, L-NAME, verapamil, atropine or pyrylamine. A comparative chromatographic profile of these extracts was also done to indicate the most abundant flavonoids presents in methanol extracts of both subspecies.

RESULTS: AMM, but not AMX, induced a contractile effect in the guinea pig ileum. This spasmogenic effect was partially inhibited by atropine, antagonist of muscarinic receptors; and pyrilamine, antagonist of H1 receptors. In contrast, AMX, but not AMM, diminished the contractions induced by KCl, EFS or ACh. The spasmolytic activity of AMX was partially inhibited by hexamethonium, ganglionic blocker; and indomethacin, inhibitor of the synthesis of prostaglandins; but not by L-NAME, inhibitor of nitric oxide synthase. In addition, AMX diminished the maximal contraction induced by CaCl2 in a calcium-free medium. Chromatographic analyses of these methanol extracts showed the presence of acacetin and tilanin in both.

CONCLUSIONS: These results suggest that in folk medicine only AMX should be used as spasmolytic, and not in combination with AMM as traditionally occurs, due to the spasmogenic effects of the latter. In addition, activation of nicotinic receptors, prostaglandins and calcium channels, but not nitric oxide mechanisms, could be responsible for the spasmolytic activity of AMX. On the other hand, release of ACh and histamine could be involved in the spasmogenic effect induced by AMM. Acacetin and tilanin are present in methanol extracts of both subspecies and both flavonoids were more abundant in AMX than AMM. Our findings contribute to the validation of the traditional use of Agastache mexicana in relieving gastrointestinal disorders, but indicate that the subspecie that should be used for this effect is A. mexicana ssp. xolocotziana.