Evaluation of anti inflammatory and antioxidant potentials of zingiber wightianum Thwaites (Malayayinchi) an ethnomedicinal plant of Kerala

Abstract

The thesis entitled ‘Evaluation of anti-inflammatory and antioxidant potentials of Zingiber wightianum Thwaites (Malayinchi), an Ethnomedicinal plant of Kerala.’ was carried out in the Ethnomedicine and Ethnopharmacology Division of Jawaharlal Nehru Tropical Botanic Garden and Research Institute (JNTBGRI), Palode, Thiruvananthapuram during the academic year 2019-2020. The objective of the study was to scientifically evaluate anti-inflammatory and antioxidant properties of an ethnomedicinal plant Zingiber wightianum Thwaites (Malayinchi). Zingiber wightianum Thwaites (Malayinchi), herbaceous plant of the family Zingiberaceae, is one of the important medicinal plants seen in dense tropical forests of the southern Indian peninsula. The rhizomes of Zingiber wightianum were collected from the hills of Western Ghats and maintained at JNTBGRI to conduct pharmacological studies. Extraction procedures were carried to prepare the drugs of different doses for the study. Acute oral toxicity studies in mice and anti-inflammatory studies in rats, were done as pharmacological analysis. In the preliminary phytochemical investigation, rhizomes of Zingiber wightianum have shown the presence of secondary metabolites like phenols, saponins, flavonoids, glycosides, phlobatannins, anthocyanins and steroids which may be responsible for its medicinal properties. The total phenolic content in the ethanolic, hydro ethanolic and aqueous extract of Zingiber wightianum, expressed as gallic acid equivalents per gram of dry extract, was 10.3, 9.9 and 9.1 mg per gram of the extract respectively. The total flavonoid content of EZW, HZW and AZW was found to be 7.5, 6.8 and 6.5 mg GAE/g of extract. Oral administration of 50, 150, 450, 1000 and 2000 mg/kg body weight of rhizome extract to Swiss albino mice for 14 days did not produce any toxic symptoms, even at the highest dose. Anti-inflammatory potential of rhizome extract was investigated in vivo by carrageenan induced paw oedema and formalin induced paw oedema methods and in vitro by Albumin denaturation assay and HRBC membrane stabilization assay. The extracts were administered at doses of 50, and 100 mg/kg body weight orally in adult wistar rats and the maximum percentage inhibition of paw oedema in the right hind limb was shown by EZW 100 mg/kg in both the methods. EZW at higher concentration protected significantly the hypotonicity induced haemolysis of HRBC and prevented the denaturation of albumin by in vitro anti-inflammatory analysis. The antioxidant effect of ethanolic, hydro ethanolic and aqueous extract of Z. wightianum showed IC50 of 121.83 μg/mL, 123.67 μg/mL and 132.66 μg/mL in hydroxyl radical scavenging assay, 86.27 μg/mL, 69.85 μg/mL, 135.82 μg/mL in nitric oxide radical scavenging assay. While in superoxide radical scavenging assay, ethanolic, hydro ethanolic and aqueous extract of Z. wightianum showed IC50 of 21.32μg/mL, 53.15 μg/mL and 44.28 μg/mL. In ABTS radical scavenging assay, of ethanolic, hydro ethanolic and aqueous extract of Z. wightianum showed IC50 of 132.77 μg/mL, 180.28 μg/mL and 190.86 μg/mL. While in DPPH radical scavenging assay, ethanolic, hydro ethanolic and aqueous extract of Z. wightianum showed IC50 of 71.02 μg/mL, 137.48 μg/mL and 137.94 μg/mL. Total antioxidant capacity of ethanolic, hydro ethanolic and aqueous extract of Z. wightianum was found to be 83 μg AAE/g, 81 μg AAE/g and 69 μg AAE/g of dry extract. The ferric reducing ability of ethanolic, hydro ethanolic and aqueous extracts of Z. wightianum were found to be 414 mg, 410 mg and 385.25 mg /g dry weight. The antioxidant potential of Z. wightianum was compared with a standard and the outcome portrayed a significant impact. These results may offer assistance to set up a comprehensive investigation utilizing the drug as the reference. Thus the above findings scientifically validated the traditional claim of Zingiber wightianum for its medicinal use.