Allelopathic effects on cowpea ( Vigna unguiculata (L.) Walp) plant and cytotoxic activities of sterols and triterpenes isolated from Justicia anselliana (NEES) T. Anders

Purification of the allelopathic ethanol extract of Justicia anselliana aerial part led to the isolation of three known compounds: two sterols (stigmasterol and β-sitosterol) and one triterpene (lupeol). Their structures were determined by analysis of spectroscopic data and confirmed by GC/MS analysis. All isolated compounds were tested for their allelopathic effects on cowpea (Vigna unguiculata) growth and for their cytotoxic activity on human (HeLa, WI-38 and Mel-43) and mouse (J774) cells. All isolated compounds showed an inhibitory effect on the three parameters measured on cowpea (Vigna unguiculata) germination (rate of germination, shoot length and fresh weight). The highest rate of inhibition of cowpea=s germination was observed with 200 ppm of lupeol (-28.4 % ± 0.7%) whereas all three parameters were inhibited very meaningfully by 200 ppm stigmasterol (-26.6% ± 0.5%; -24.2% ± 0.7% and -21.1% ± 0.7% respectively for germination, shoot length and fresh weight of Vigna unguiculata (L.) Walp). None of the isolated compounds was toxic on J774 (murine macrophages), WI-38 (human lung fibroblasts), human HeLa (human cervix carcinoma cells) and melanoma Mel-43 cell. This is the first report of the allelopathic activities of lupeol, stigmasterol and β-sitosterol on cowpea (Vigna unguiculata).