Investigations of the methanolic leaf extract of Costus after. Ker for pharmacological activities in vitro and in vivo.

Summary

The methanolic leaf extract of Costus afer. Ker (family: Zingiberaceae) was investigated for some pharmacological effects in vivo and in vitro. Brine shrimp lethality test showed that the extract was significantly (p < 0.05) cytotoxic with L[C.sub.50] of 21.3 ppm. The extract showed moderate local anesthetic property, about twice less than lignocaine of the same concentration, on guinea pig wheal test. The extract contracted the guinea pig ileum in a concentration-dependent manner, but had no effect on pleuripara and nullipara non-gravid uteri at progestogenic and estrogenic phases respectively. The contractile effect on the guinea pig ileum was partially inhibited by atropine but completely reversed by adrenaline.

The extract induced expulsion of whole fetuses still enveloped within the placental membrane at the 3rd trimester of pregnancy. The extract exhibited a biphasic antihyperglycemic activity. At 200 mg/kg body wt., p.o., it decreased the blood glucose level by 50% in Streptozotocin-induced hyperglycemia in male rats in 60 minutes post dosing.

However, doses above 200 mg/kg body wt., p.o., caused increase in blood glucose level, potentiating the action of STZ. At 10 [micro]g/ml the extract induced about 98% glucose uptake in differentiated 3T3-L1 adipocytes when compared with insulin (340 nm).

Key words: local anaesthetic, abortificient, antihyperglycemia, glucose transport, 3T3-L1 adipocytes, Costus afer. Ker

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Introduction

Costus afer. Ker (Family: Zingiberaceae) is a tall perennial herbaceous, unbranched medicinal plant with creeping rhizome, commonly found in moist or shady forests and riverbanks of tropical West Africa including Nigeria, Ghana and Cameroon (Iwu, 1983). The plant is commonly known as gingerlily. It is known as "Okpete" or "Okpoto" in Igboland, "Kakizawa" in Hausa "tete-egun" in Yoruba and "Mbritem" in Efik all in Nigeria (Iwu, 1983). Anglophone Cameroon calls it "Monkey sugar cane".

This plant and other species of the genus are used as remedy for cough, inflammation, arthritis, as laxative, aparient and purgatives, diuretics, rheumatism and treatment of several diseases (Oliver, 1960). In Nigeria, the plant extract is used as fodder to treat goats with retained placenta. Mystically, the plant is used in the preparation of charms, fetish and ritual ornaments (Iwu 1982). The decoction of the stem or powdered fruits is used as cough medicine. Whole boiled root is applied to cuts and sores, and soothing fomentation for rheumatic pains prepared with boiled leaves (Oliver, 1986; Iwu and Anyanwu 1982, 1982a). It reduced carageenan-induced edema in the rat paw, checked diarrhoea caused by arachidonic acid and castor oil (Awouters et al. 1978). It ameliorated all signs associated with adjuvant-induced polyarthritis in rats and a dose of 100-300 mg/kg daily is well tolerated in human (Awouters et al. 1978). In Ohafia, Abia State Nigeria and in some parts of Anglophone Cameroon, the decoction of the plant is given to diabetic patients to alleviate the clinical signs (Oral communication).

Other species of the genus also have medicinal effects e.g. Costus lucanusianus is used in the Ivory Coast for the treatment of impending threatened abortion (Foungbe et al. 1987). It also exhibits uterine relaxant activity. Costus schlechteri and C. afer are used in the treatment of diabetes mellitus (Ampofo, 1977; Iwu 1993). Preliminary phytochemical screening of the extract revealed the presence of saponins, cyanogenic glycosides, tannins, flavonoids and carbohydrates.

Phytochemical reports indicate that the genus Costus is rich in steroidal saponins, sapogenins, oxalates, furans, furan derivatives and starches (Oliver, 1986). The TLC of the tubers extracted with petroleum ether and chloroform yielded lanosterol, tigonenin and diosgenin. Iwu (1982) isolated costugenin and sapogenin from the chloroform extract of the plant. Based on the reported biological activities of the extracts from C. afer the present study was designed to investigate the pharmacological activities of the methanolic leaf extract of Costus afer. Ker.

Materials and Methods

Plant material

The leaves of Costus afer were collected from "Onu-Uduma" riverbank in Ebem Ohafia, Abia State, Nigeria, in July …