LARVICIDAL PROPERTIES OF SIMALIKALACTONE D FROM QUASSIA AFRICANA (SIMAROUBACEAE) BAILL AND BAILL, ON THE MALARIA VECTOR ANOPHELES GAMBIAE

Background: Botanical and microbial insecticides have been increasingly used for the control of mosquito given their efficacy and documented non-toxic effects on non-target organisms. The discovery of new insecticides is imperative because of the development of resistance by the mosquitoes to the readily available insecticides. The aim of this study was therefore to isolate and characterize compounds from a local medicinal plant, Quassia africana Baill and Baill (Simaroubaceae) that were toxic to Anopheles gambiae. Material and methods:The methanol extracts of the leaves, stem and roots of Quassia africana were tested against fourth instar larvae of An. gambiae. The root extract was partitioned into hexane, chloroform and ethyl acetate and the resulting extracts screened for larvicidal properties. The extracts and the fraction with the highest bioactivity were subjected to repeated column chromatography and isolated compounds evaluated for potential toxicity to An. gambiae larvae. The structure of the active compound was elucidated using spectroscopic techniques. The root extract showed the strongest activity profile (LC50 = 17.58 μg/mL). The chloroform soluble fraction obtained after partitioning the crude extract into solvents based on polarities was the most toxic. Further bio-activity-guided chromatographic separation of the chloroform fraction of the root extract led to the identification and isolation of a simalikalactone D as the larvicidal compound in Q. africana (LC50 = 1.25 μg/mL). Results: Results suggest that Q. africana may serve as a source for vector control agent for malaria. Conclusion: Simalikalactone D was identified as the larvicidal compound in Q. africana (LC50 = 1.25 μg/mL)

Bioassay-guided isolation of cytotoxic constituents of Aframomum melegueta K.Schum. seeds

The seeds of Aframomum melegueta are used extensively in the Nigerian ethnomedicine for the management of cancer. This study therefore aimed at isolating and characterizing its cytotoxic constituents. Methanol extract of the seed was obtained through cold maceration, and it was further partitioned into n – hexane, dichloromethane and ethylacetate. The most active fraction was purified on repeated chromatographic techniques, using vacuum liquid chromatography (VLC), column (CC), and high-performance liquid chromatography (HPLC). The extract, purified fractions and isolated compounds were tested for their cytotoxic activities against the human Rhabdomyosarcoma (RD) and breast (MCF-7) cancer cell lines, using MTT assay. The crude extract and n-hexane fraction were found to be selectively cytotoxic to the cancer cell lines. Bioassay-guided fractionation of the n-hexane fraction led to the isolation of three compounds, which were identified as 6-shogaoal, 6-paradol, and 1-dehydro-6-gingerdione.  6-shogaoal   demonstrated the highest cytotoxicity with CC50 values of 0.11 ± 0.02 and 0.25 ± 0.05ìg/mL against RD and MCF-7 cell lines  respectively, and these were higher in activity when compared with cyclophosphamide (CC50 = 1.98 ± 0.15 and 0.71 ± 0.7ìg/mL). The presented data validates the  ethnomedicinal use of A. melegueta in the treatment of cancer and is also indicative of the potential of 6-shogaol as an anticancer agent