Phytochemical Screening and Biological Activities of Methanolic Extracts of Selected Species of Swertia L.

Abstract

Swertia is a genus of traditionally used plants pertaining to the family Gentianaceae. There are about 250 species of Swertia L. worldwide out of which 28 species (including three endemic species) with five varieties are reported from Nepal. In the present study, five species comprising eight samples were tested for their phytochemical constituents and biological activities. Methanol was used as solvent and sonication was used for extraction process. In quantitative assay, the total phenolic content and total flavonoid content was measured using Folin-Ciocalteu reagent and Aluminium chloride colorimetric method. In biological assay, antioxidant activity was determined by DPPH Radical Scavenging Assay method, α-glucosidase activity by using PNPG solution and antibacterial activity by agar well diffusion method. Column chromatography method was used for separation of samples into fractions using series of solvents. The highest yield percentage was obtained from S. multicaulis roots (35.67±3.52%) while lowest from S. chirayita (12.79±2.23%). Qualitative phytochemical analysis of selected species of Swertia showed the presence of alkaloids, saponins, phenols, flavonoids, steroids, tannins and terpenoids. The total flavonoid content was found to be highest in S. multicaulis leaves (54.13±0.002mg QE/g) and lowest in S. multicaulis root (7.67±0.001 mg QE/g). Highest amount of total phenol content was found in S. barunensis leaves (107.38±2.35 mg GAE/g) and lowest in S. cuneata (37.44±2.28mg GAE/g). In DPPH scavenging assay lowest IC50 value was observed in S. barunensis leaves with value i.e, 17.74 μg/mL while highest IC50 value was observed in S. nervosa i.e, 399.84 μg/mL. In α-glucosidase assay, highest inhibitory activity was observed in S.barunensis leaves (36.65±0.74%) while lowest in S. cuneata (-26.15±0.3%). The fractionated sample of S. barunensis and S. multicaulis leaves when tested for their αglucosidase

inhibition activity fraction E exhibited maximum inhibition activity (97.2±1.86%) in S. barunensis leaves while fraction G (94.4±0.66%) in S. multicaulis leaves. The antibacterial activity was carried out against five bacterial strains. None of the plant sample showed inhibition against all the strains. S. barunensis leaves showed best antibacterial activity against Bacillus subtilis that can be comparable with the standard drugs Gentamycin. The fractionated sample of S. barunensis and S. multicaulis leaves when tested for antibacterial activity didn’t show much significant zone of inhibition. Based on the above mentioned results, it can be concluded that Swertia species are rich in medicinal properties and are needed to further research and explore on more species of Swertia which can be useful in development of drugs and pharmaceutical areas.