Antibacterial and antioxidant activities of methanol extract and fractions of Clerodendrum viscosum Vent. leaves

Abstract

The present study was undertaken to evaluate antimicrobial and antioxidant activities of methanol extract as well as n-hexane, chloroform, ethyl acetate and aqueous fractions of Clerodendrum viscosum Vent. leaves. The antimicrobial activity, total phenolics and flavonoids were determined by agar-well diffusion, Folin–Ciocalteu and aluminum chloride colorimetric methods, respectively The antioxidant potential was evaluated by using various in vitro methods such as 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2, 2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), nitric oxide and hydrogen peroxide radical scavenging assays. The maximum inhibition zones for S. aureus, B. subtilis, E. coli, K. pneumoniae and P. aeruginosa were 27, 25, 28, 23 and 22 mm for ethyl acetate fraction, respectively, whereas n-hexane fraction of methanol extract showed the weakest antimicrobial activity with inhibitory effect against B. subtilis and K. pneumoniae. The total phenolic content (TPC) in ethyl acetate fraction (87.28 mg GAE/g) was highest, followed by methanol extract (76.75 mg GAE/g), aqueous fraction (61.36 mg GAE/g) and chloroform fraction (28.46 mg GAE/g), respectively. The total flavonoid content (TFC) was in order of ethyl acetate fraction (77.48 mg quercetin equivalent/ g) > methanol extract (64.56 mg quercetin equivalent/ g) > aqueous fraction (49.66 mg quercetin equivalent/g) > chloroform fraction (32.85 mg quercetin equivalent/ g). The ethyl acetate fraction of methanol extract of C. viscosum leaves showed moderate free radical scavenging activity as evidenced by IC₅₀ values in DPPH (64.51μg/mL), ABTS (28.32μg/mL), nitric oxide (80.02μg/mL) and H₂O₂ (77.45μg/mL) scavenging assays. The results of present study showed that C. viscosum leaves possess high phenolic, flavonoid contents, potential antimicrobial and antioxidant activity and could be a potential source of natural antioxidant that could have great importance as therapeutic agents in preventing or slowing the progress of ageing and age associated oxidative stress related degenerative diseases.