Antimicrobial Activity, Toxicity and Phytochemical Screening of Lantana Trifolia Leaf Extracts

Abstract

Medicinal plants have played a significant role all over the world in preventing and healing a range of diseases. Lantana trifolia is a plant used in the management of asthma, common cold, cerebral malaria, epilepsy and tonsillitis. However, empirical data to validate its toxicity profile and safety is lacking. Thus, this study was designed to investigate the phytochemical composition, antimicrobial activity and the acute and sub-acute toxicity of extracts from L. trifolia leaves to validate its ethnomedicinal usage. This study provides information on the safety of the plant. Acute oral toxicity study of the aqueous leaf extract of L. trifolia was conducted according to guideline 423 described by the Organization for Economic Co-operation Development (OECD) whereby a single dose of the extract was given to female rats at dose levels 300mg/Kg Bwt and 2000mg/Kg Bwt. Thereafter, the rats were observed individually for the first four hours, then over a period of 24 hours and at least once daily for 14 days. Sub-acute oral toxicity of the aqueous leaf extract of L. trifolia was investigated at three dose levels of 250 mg/Kg Bwt, 500 mg/Kg Bwt, and 1000 mg/Kg Bwt in both female and male Swiss albino mice based on the OECD guideline number 407 for 28 days. The control group received distilled water. Thereafter, body weight, feed consumption and water consumption were monitored. Vital parameters of the blood such as haematological profiles and biochemical profiles were determined at the end of the experiment. Moreover, histopathological examination of the various harvested organs was done. Qualitative phytochemical analysis was performed on both aqueous and organic extracts to identify compounds of pharmacological value. The extraction yield of the aqueous and organic extracts was 5.2% and 11.2% respectively. Qualitative phytochemical screening of the extracts showed the presence of tannins, saponins, phenolics, terpenoids, flavonoids, alkaloids and reducing sugars in both extracts. In an acute oral toxicity study, the aqueous leaf extract of L. trifolia demonstrated a median lethal dose (LD50) of >2000 mg/Kg Bwt, depicting its safety. Following subacute oral toxicity, the urea levels in female mice which received 1000 mg/Kg Bwt dose of the aqueous leaf extract of L. trifolia were significantly elevated compared to those of the control group mice (P<0.05). Moreover, there was no significant difference in the mean body weight between the treated and control groups(P>0.05). Treatment groups that received 1000mg/kg body weight of the aqueous extract demonstrated diffuse tubular epithelium degeneration, indicating nephrotoxicity and a dose-related hepatocyte degeneration, indicating hepatotoxicity Staphylococcus aureus (Gram-positive), Bacillus cereus (Gram-positive), Escherichia coli (Gram-negative) and Candida albicans(fungus) were used to determine the antimicrobial activities of aqueous and DCM-methanol extracts. The most susceptible microorganism in the current study was C. albicans. The minimum inhibitory concentration and minimum bactericidal concentration values of aqueous and organic leaf extracts of L. trifolia for S. aureus were 200mg/ml and 400mg/ml; 3.12mg/ml and 6.25mg/ml respectively. The MIC and MFC for C. albicans were 100mg/ml and 3.125mg/ml for both aqueous and organic extracts. The aqueous leaf extract of L. xiv trifolia may be relatively non-toxic when administered orally for a short period. This is supported by a higher LD50 which was determined to be >2000mg/kg body weight. There is need to monitor the liver, kidneys, haematological and biochemical parameters especially when higher doses are administered for a long time since deleterious dose-dependent effects can result. Various phytochemical constituents were present in the L. trifolia leaf extracts hence this could form the basis for the discovery and development of novel drugs.