Methanolic extracts and different fractions of whole plants of Leucas zeylanica show promising analgesic and antioxidative activities

Abstract

Background and objective Leucas zeylanica is a medicinal plant used traditionally in tropical Asian countries including Bangladesh. This study was conducted to assess the pharmacological activities of whole plants of L. zeylanica. Materials and methods Methanolic crude extracts (MCEs) and petroleum ether-soluble fractions (PESFs), chloroform-soluble fractions (CSFs), and ethyl acetate-soluble fractions (EASFs) of whole plants were studied for the probable peripheral analgesic, central analgesic, and antioxidant and antimicrobial activities by acetic-acid-induced writhing and radiant heat tail-flick tests in mice, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, and disk diffusion method, respectively. Results and conclusion The MCEs showed the highest peripheral analgesic activity among the test samples with an inhibition of pain sensation of 40% (at 200 mg/kg body weight dose, MCE200) and 32% (at 100 mg/kg body weight dose, MCE100) in comparison to diclofenac sodium (66.67%, P<0.001). In central analgesic activity test, elongation of flicking time was calculated at 30, 60, and 90 min of administration of test samples where morphine was the positive control. All extracts and fractionates showed significant increase in tail-flicking time. However, methanolic extract showed the highest activity (at 60 min) among all test samples (15.44±0.256, P<0.001). In antioxidant tests, butylated hydroxytoluene (BHT) was used as the positive control where methanolic extracts exhibited the highest antioxidant potentials among the test samples. IC50 (μg/ml) values were 19.61 (BHT), 28.46 (MCE), 65.61 (EASF), 84.75 (PESF), and 97.09 (chloroform-soluble fractions). Additionally, whole plant extracts showed weak antimicrobial activity. This ethnopharmacological investigation suggests that methanolic extracts and different fractions from L. zeylanica have strong analgesic and antioxidant potential and can be a significant source of natural medicine.