PHARMACOLOGICAL EFFECTS OF HARPAGOPHYTUM PROCUMBENS DC [PEDALIACEAE] SECONDARY ROOT AQUEOUS EXTRACT ON ISOLATED GASTRO-INTESTINAL TRACT MUSCLES OF THE CHICK, GUINEA-PIG AND RABBIT

Abstract

In an attempt to scientifically appraise the ‘healing powers’ and medicinal value of Harpagophytum procumbens DC [family: Pedaliaceae], and throw some light on the efficacy and safety of the medicinal plant product, we have examined the pharmacological effects of the plant’s secondary root aqueous extract (HPE) on the chick, guinea-pig and rabbit isolated gastro-intestinal smooth muscle preparations. The results of this laboratory animal study indicate that relatively low to high doses of Harpagophytum procumbens secondary root aqueous extract (HPE, 10–1000 µg/ml) provoked concentration-related, significant (P<0.05–0.001), atropine-sensitive contractions of the chick isolated oesophagus and guinea-pig isolated ileum. Relatively moderate to high concentrations of the plant’s extract (HPE, 200–1000 µg/ml) usually induced concentration-dependent, biphasic responses in the rabbit isolated duodenum. Relatively low concentrations of the plant’s extract (HPE, 10–100 µg/ml) usually produced an initial slight, transient and non-significant (P>0.05) increase in the amplitude of the spontaneous, myogenic, rhythmic, pendular contractions of the rabbit duodenal muscle preparations. On the other hand, relatively moderate to high concentrations of the plant’s extract (HPE, 200–1000 µg/ml) always produced initial slight, significant (P<0.05–0.01) reductions (inhibitions) of contractile amplitudes of the rabbit isolated duodenum. The initial slight depressions of the contractile amplitudes of the isolated rabbit duodenum caused by relatively moderate to high concentrations of the plant’s extract (HPE, 200–1000 µg/ml) were always followed by concentration-related, significant (P<0.05–0.001) elevated baseline tones (tensions) and augmentations of the contractile amplitudes; followed by secondary, longer-lasting relaxations and reductions of the contractile amplitudes of the spontaneous, rhythmic, myogenic, pendular contractions of the rabbit isolated duodenal muscle preparations. In a separate set of experiments involving the use of chick isolated biventer-cervicis and oesophagus muscle homogenates for colorimetric anticholinesterase determination, Harpagophytum procumbens (HPE, 10–1000 µg/ml) was found to possess anticholinesterase activity. In this regard, however, the plant’s extract was found to be less potent than physostigmine. The anticholinesterase action of the plant’s extract is speculated to contribute, at least in part, to the contractile effects of the herb’s extract on the isolated gastro-intestinal smooth muscle preparations used. The results of this laboratory animal study indicate that H. procumbens secondary root aqueous extract (HPE) induced concentration-related contractions of gastro-intestinal tract smooth muscles. These findings may account for the commonly reported adverse effect of ‘gastro-intestinal discomfort or upset’ usually associated with Harpagophytum procumbens secondary root extract medication.