In Vitro Antibacterial Activity of Essential Oils from Tithonia Diversifolia Leaves and Flowers Against Ralstonia Solanacearum

Abstract

Bacterial wilt disease caused by Ralstonia solanacearum is a major constraining factor in the production of tomatoes in Kenya, leading to an overreliance on synthetic pesticides. As a result, there is increased research on bio-pesticides as safer alternatives. The present study, therefore, characterized and evaluated in 524 European Journal of Applied Sciences (EJAS) Vol. 10, Issue 2, April-2022 Services for Science and Education – United Kingdom vitro antibacterial activity of essential oils from Tithonia diversifolia leaves and flowers against R. solanacearum. Hydrodistilled essential oils were characterized through Gas Chromatography-Mass spectrometry (GC-MS) while functional groups were confirmed using Fourier Transform Infrared Spectroscopy (FT-IR). Antibacterial activity was performed using the disc diffusion method and minimum inhibitory concentration evaluated using broth dilution. Hydrodistilled leaves of T. diversifolia yielded 0.18 + 0.08 % (v/w); 0.10 + 0.07 % w/w as compared to 0.15 + 0.09 % (v/w); 0.08 + 0.03 % w/w in the leaves . GC-MS profiling revealed the major compounds were (Z,Z,Z)-9,12,15- Octadecatrienoic acid ethyl ester(18%), palmitic acid (16%), spathulenol (12%), Cis- 9,12,15- Octadecatrienoic acid (8.14%), tetrateracontane (6%) and 1-Octen-3yl-acetate (5.22%) in the leaves ad α-linolenic acid trimethylester(33%), Z,Z Hexadecadienoic acid(26%), octadecanoic acid trimethylester (9%), palmitelaidic acid (8.49%), Germacrene D(5.45%), azelaic acid (5.02%) and caryophyllene oxide (5.00%) in the flowers. Antibacterial activity showed that T. diversifolia essential oils had mean inhibition zones of 12.61+ 0.22 mm and 11.82 + 0.76 mm from the leaves and flowers respectively, in comparison to metham sodium which gave inhibition zone of 25.78 ±0.29 mm (p = 0.001). Based on the results, this study gives credence to T. diversifolia essential oils as viable antibacterial agents.