Chemical Compositions, Antioxidant and Anti-diabetic Activities of Root Wood and Root Bark Essential Oils from Pterocarpus soyauxii TAUB.

Abstract

The chemical composition of essential oils (EOs) isolated by hydrodistillation from Pterocarpus soyauxii Taub. root wood and root bark were determined for the first time by GC/MS analysis. The EOs gave a percentage yield (w/w) of 0.34 % and 0.31 % for root wood and root bark respectively. A total of 60 compounds accounting for 86.1 % of the root wood EO composition were identified with monoterpenes (45.4 %) and sesquiterpenes (14.7 %) as predominant constituents. Root bark EO gave 53 identified constituents which make up about 78.5 % of the EO dominated by non-terpenes (23.4 %) and alkanes (14.1 %). The EOs are good sources of limonene (16.9 %), γ-terpinene (9.8 %) and p-cymene (6.70 %). The anti-diabetic (α-amylase and α-glucosidase models) and antioxidant activities (DPPH and H2O2 models) of EOs were evaluated in comparison with standard drugs. Alpha-amylase inhibition gave IC50 values (mg/mL) of 0.0493 and 0.0471 for root wood and root bark EOs respectively, compared to acarbose the standard anti-diabetic drug (0.0401) while α-glucosidase assay gave IC50 values (mg/mL) of 0.0517 and 0.0486 for root wood and root bark EOs respectively, compared with acarbose (0.0418). In the DPPH antioxidant assay, root bark EO showed higher activity (0.157 mg/mL) compared to root wood EO (0.159 mg/mL) while Root wood and root bark EOs had IC50 values (mg/mL) of 0.157 and 0.171 respectively using the H2O2 model. Results revealed the presence of chemical constituents in the EOs which could be responsible for activities expressed by the plant.