Phenolic compound and antioxidant levels of Prismatomeris glabra

Abstract

A decoction of the roots of Prismatomeris glabra (PG), family Rubiaceae, has been traditionally used by rural people for wellness effects. However, there are no scientific data to support the folkloric use of this plant. This research was thus conducted to determine whether aqueous extract of PG roots possess antioxidant capacity. PG extract was prepared by boiling powdered roots for 10 minutes before drying in a spray dryer. Antioxidant capacity was determined using photochemiluminescent method, DPPH radical scavenging assay, ferric reducing antioxidant power (FRAP) assay, tert-butyl hydroperoxide (tert-BOOH) induced lipid peroxidation assay and by measurement of the end product of lipid peroxidation, malondialdehyde, produced in vivo. Antioxidant studies showed that PG did not possess high antioxidant capacity as compared to phenolic antioxidant standards. In vitro, lipid- and water-soluble antioxidant capacities of PG were 36.61±1.39 I¼g/mg of ascorbic acid equivalent and 8.28±1.23 I¼g/mg of trolox equivalent, respectively. Total phenolic content of the extract was 6.82±0.71%. PG scavenged DPPH radicals, reduced ferric ions and inhibited tert-BOOH-induced lipid peroxidation with values of 239.31±70.48 µg/ml (EC50), 0.298 ± 0.026 µmol Fe2+/mg and 188.7±15.3 (IC50), respectively. In vivo, PG (500 mg/kg/d, p. o., acute and 7-day daily dosing) did not affect malondialdehyde levels of major organs and plasma. In conclusions, aqueous extract of PG roots possess about a third the antioxidant capacity of ascorbic acid and a tenth the antioxidant capacity of trolox, a vitamin E analogue. Thus, PG roots may not be an important source of antioxidants, although it apparently has sufficient antioxidant capacity to enhance wellness.