Analysis of Total Phenolic, Terpenoid Contents, and Antioxidant Activity of Commiphora mollis (Oliv.) Engl. Resin

Abstract

Commiphora mollis (Oliv.) Engl. (Burseraceae) is a well-known medicinal plant and widely practiced by traditional healers in Borena Oromo society, Oromia regional state, Ethiopia for the treatments of wounds, stomach ache, and skin disorder. Therefore, this study aimed to investigate the total phenols, terpenoid contents, and antioxidant property of the C. mollis resinous exudate. C. mollis resin exudate was extracted with petroleum ether, chloroform, and methanol that yielded 27.46 ± 0.48, 46.56 ± 0.42, and 53.00 ± 1.39 % of the dry sample, respectively. Qualitative phytochemical analysis of the extracts revealed the presence of alkaloids, terpenoids, phenols, and saponins. The total phenolic contents of extracts were analyzed by the Folin-Ciocalteu redox method. Absorbances were measured at the experimentally determined maximum absorption wavelength (765 nm), after 30 of contact time between the extracts or standard and the reagent. The analysis showed that all the extracts are rich in phenolic compounds with the highest amount (112.24 ± 1.67 mg/g) observed in methanol extract. On the other hand, the total terpenoid content is high in chloroform (86.67 ± 3.82 %), and petroleum ether (75.0 ± 2.5%) extracts than the methanol extract (27.50 ± 2.50 %). This could be due to the less polar nature of terpenoids that can be extracted more by a less polar solvent such as chloroform and petroleum ether than methanol. Whereas the reverse could happen when it comes to phenolic compounds, as they are polar and thereby extracted more with methanol. The antioxidant activity and kinetics of the reaction was also determined using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay at 517 nm. It was observed that methanol extract and ascorbic acid displayed very fast reaction kinetics reaching the steady state of reaction at 0.288 to 0.545 min and 1.82 to 2.19 min, respectively, while chloroform and petroleum ether extracts showed low antiradical activity with the steady state time of 33.18 to 76.96 min and 25.74 to 47.21 min, respectively. At 60 min reaction time, methanol, chloroform, and petroleum ether extracts showed DPPH radical scavenging activity with IC50 values of 254.8 ± 1.08, 296.5 ± 2.76, and 316.70 ± 1.16 μg/mL, respectively. The high radical scavenging activity of the methanol extract than chloroform and petroleum ether extracts could probably be due to the high phenolic contents of methanol extract (as indicated by the phenolic analysis). For better understanding, further study accompanied by isolation and structure elucidation of pure compounds is recommended.