Author(s):

Md. Rubel Rana, Nowrin Islam Amin, Abdullah An Naser and Nurul Islam

Abstract: Biological activities of Petroleum ether (Pet. ether), CHCl_3, CH₃OH and EtOAc extracts of Amoora rohituka leaf were tested against the red flour beetle Tribolium castaneum (Hbst.) adults for dose-mortality and insect repellent activity; against eggplant aphid Aphis gossypii Glover for repellent activity; against brine shrimp Artemia salina L. nauplii for cytotoxicity; against larvae of Culex quinquefasciatus Say for larvicidal activity; and against five bacteria and fungi for anti-microbial activity. The dose-mortality observed for Pet. ether, EtOAc and CHCl₃ extracts with LD₅₀ values 1.769, 1.049, 0.871 and 0.249mg cm^-2; 2.099, 1.047, 0.927 and 0.819mg cm^-2; and 2.847, 2.126, 2.053, 1.806mg cm^-2 for 12, 24, 36 and 48h of exposure respectively, whereas CH₃OH extract did not show any mortality against the adult beetles of T. castaneum. The CHCl_3, CH₃OH and EtOAc extracts showed promising repellent activity against T. castaneum adults at P<0.001, P<0.01 and P<0.05 levels of significance respectively, while the Pet. ether extract did not show repellent activity at all. Against eggplant aphid CH₃OH extract showed strong repellent activity (P<0.001) while EtOAc and CHCl₃ extracts were found moderately active (P<0.01) whereas Pet. ether extract did not show any repellency. The similar extracts responded through Brine shrimp lethality assay where CH₃OH extract found most effective (LD₅₀ values 1302.933, 343.255, 295.546ppm and 100% mortality observed after 24h exposure) followed by Pet. ether extract (LD₅₀ 245.577, 279.807, 89.122 and 39.884ppm), EtOAc extract (LD₅₀ values 3796.668, 224.936, 155.737 and 57.643ppm) and CHCl₃ extract (LD₅₀ -, 749.721, 366.104 and 62.413ppm) for 6, 12, 18, and 24h of exposure respectively. In case of larvicidal activity test against 1^st instar larvae Culex quinquefasciatus the highest lethality perceived for Pet. ether extract (LC₅₀ 340.501, 268.464, 118.579, 53.279 and 33.261ppm) followed by CHCl₃ extract (LC₅₀ 2605.863, 1045.340, 566.034, 211.233 and 137.335ppm) and EtOAc extract (LD₅₀ 551.542, 506.756, 384.259, 239.025 and 162.077ppm) for 6, 12, 18, and 24h exposure respectively; while CH₃OH extract did not show any activity. These four extracts were also propitious against five pathogenic bacteria (Agrobacterium sp., Bacillus cereus, Escherichia coli, Shigella dysenteriae and Staphylococcus aureus) at concentrations of 200 and 400μg/disc while a standard Penicillin 30μg/disc and three pathogenic fungi (Aspergillus niger, Candida sp. and Saccharomyces sp.) at concentrations of 50 and 200μg/disc with a standard Nystatin 10μg/disc were also used for comparison. CH₃OH extract showed the highest antibacterial activity with the inhibition zone of 19mm and 30mm respectively against E. coli bacteria in comparison to others while EtOAc extracts showed the highest antifungal activity with the inhibition zone of 12mm and 21mm respectively against Candida sp. The results revealed the potentiality of A. rohituka leaf extracts for the control of flour beetles, aphids, mosquito larvae, bacteria and fungi.

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