Pharmacological and chemical screening of Byrsonima crassifolia, a medicinal tree from Mexico. Part I.

Leaf and bark extracts of Byrsonima crassifolia displayed concentration-dependent, spasmogenic effects on rat fundus in vitro and biphasic effects on rat jejunum and ileum in vitro. Dose-related in vivo effects in intact rats using hippocratic screening were: decrease in motor activity, mild analgesia, back tonus, enophthalmos, reversible palpebral ptosis, ear blanching, Robichaud positive, catalepsy (awake) and strong hypothermia. Rat fundus in vitro was used as the bioassay to carry out an activity-directed separation. Bioactive material was concentrated in a 2% acetic acid leaf extract (HOAcE). Potency of HOAcE was increased by the presence of pargyline in the bathing solution. HOAcE was antagonized noncompetively by 1(1-naphthyl) piperazine (1-NP) and cyproheptadine and antagonized competitively by atropine (ATR). Cumulative concentration-response curves of HOAcE and serotonin (5-HT) did not show significant departure from parallelism (P > 0.1) and 5-HT potency was 6040 times that of HOAcE (95% confidence limits: 4620-7850). Solvent extraction of HOAcE split the spasmogenic activity of HOAcE into two types: (i) high-efficacy, low-potency, n-butanol-extracted, pargyline- and 1-NP-sensitive, ATR-insensitive activity, and (ii) low-efficacy, high-potency, ethyl acetate-extracted, pargyline-insensitive, ATR- and 1-NP-sensitive activity. HOAcE lacked muscarinic and nicotinic effects on rat jejunum and frog rectus abdominis. Results suggest the presence of more than one spasmogenic compound in the plant.