Phytochemical Investigation, Antibacterial And Antioxidant Activities Of Root Barks Extract Of Gnidia Involucrate

Abstract

Gnidia involucrata (Thymelaeaceae) is a plant in the genus Gnidia. It is used as laxative, rheumatism, insecticides, insect repellant and antimalarial. In view of its traditional uses, the root barks were extracted successively with hexane, EtOAc and MeOH to afford 0.78% hexane, 4% EtOAc and 6% MeOH crude extract respectively. Phytochemical screening of the EtOAc and MeOH extracts revealed the presence of flavonoids, saponins, terpenoids, tannins and phenolics but additionally EtOAc extract revealed alkaloids. The EtOAc extract which showed good TLC profile was subjected to silica gel column chromatography separation which furnished three compounds (compound-1, compound-2 and compound-3). The compounds were found to be tetratriacontanyl caffeate, 12-O-dodeca-2,4-dienoyl phorbol-13-acetate and 5,7-dihydroxy-2-[4hydroxyphenyl] flavanone based on their spectroscopic data IR and NMR ( 1H-NMR, 13C-NMR and DEPT-135). The EtOAc extract and isolated compounds were assessed for their antibacterial activities. The results showed that the EtOAc extract displayed inhibition zone of 23, 14, 12 and 12 mm against S. aureus, E. coli,P. mirabilis and Klebsiella pneumonia, respectively. These data were significant compared with the positive control with inhibition zone of 23, 24, 21, and 19 mm against S. aureus, E. coli, P. mirabilis and Klebsiella pneumonia, respectively. Among the compounds tested, compound-2 and compound-3 showed an inhibition zone of 11 mm and 12 mm against E. coli. Furthermore, the EtOAc, MeOH extract, compound-1 and compound-2 were found to inhibit DPPH radical by 70.7%, 66.9%, 85.8% and 52.8%, respectively. The radical scavenging activity of compound-1 was comparable with that of ascorbic acid (97%) that was used as positive control in the test. The IC50, the concentration of the sample that inhibits 50% of the radical values of EtOAc and MeOH extrat, compound-1 and compound-2 were 15.3, 21.8, 2.3, and 83.6 µg/mL, respectively. The lower IC50 value displayed by compound-1 indicates its strong radical scavenging activity compared to the ascorbic acid. The antibacterial activities displayed by the root barks extract of G. involucrata corroborate the traditional use of this plant against bacterial infections.