Influence of methanol leaf extracts of Hilleria latifolia and Laportea ovalifolia on in vitro activity of selected antibiotics

Antibiotic resistance has become a major health and economic problem worldwide since it leads to treatment failure, complications and eventually death [1]. This has led to the search for newer and effective antimicrobial agents as well as resistance modifying agents. Our aim was to investigate the influence of methanol leaf extracts of Hilleria latifolia (Lam.) H. Walt. (HLML) and Laportea ovalifolia (Schumach.) Chew (LOML) on the activity of some selected antibiotics.

Minimum inhibitory concentrations (MIC) of the test antibiotics (alone), extracts only and test antibiotics in the presence of a sub-inhibitory concentration (5 mg/mL) of the extracts against selected typed strains of bacteria were determined using micro-dilution [2]. HLML and LOML exhibited antibacterial activity with MIC of 50 to 100 mg/mL against the test organisms. HLML potentiated the activity of amoxicillin (2 to 8-fold) against test organisms except Klebsiella pneumoniae and Streptococcus pyogenes, whereas LOML potentiated the activity of amoxicillin (2-fold) against Escherichia coli and Staphylococcus aureus. In addition, HLML increased the activity of ampicillin (2 and 4-fold) against E. coli and Salmonella typhi respectively, whiles LOML caused a 2 to16-fold reduction in the activity of ampicillin. Both HLML and LOML reduced the activity of erythromycin and ciprofloxacin by 2 to 16 folds (Table 1). HLML and LOML potentiated the antimicrobial activity of amoxicillin and ampicillin against some of the test organisms. The activity of erythromycin and ciprofloxacin reduced in the presence of both extracts.

Tab. 1: MIC of test antibiotics and the test antibiotics in the presence of sub-inhibitory concentration of HLML and LOML.

Antibiotics		MIC (µg/mL) Test micro-organisms
		coli	5. subtilis	5. typhi	K. pneumoniea	S. aureus	S. pvogens	P aeruginosa
	Amox	256	128	128	128	256	256	128
Amoxicillin	HLML	32	32	64	128	32	> 1024	64
	LOML	128	128	256	256	128	> 1024	128
	Ampi	128	32	128	128	64	64	64
Ampicillin	HLML	64	32	32	128	64	> 1024	64
	LOML	128	128	128	256	64	> 1024	> 1024
	Ervt	32	256	64	128	64	64	128
Erythromycin	HLML	512	1024	1024	1024	1024	512	512
	LOML	512	512	512	1024	512	1024	1024
		2	2	4	4	4	4	4
Ciprofloxacin	HLML	16	16	16	8	8	8	16
	LOML	16	32	32	32	32	16	32
Amox- amoxicillin, Ampi- ampicillin. Eryt-erythromycin and Cipr- ciprofloxacin. Sub-inhibitory concentration (5 mg/mL) of HLML and LOML.

References:

[1] Harbarth S. The effect of antimicrobial uses on emergence and selection of resistance. Anasthesiol Intensivmed Notfallmed Schmerzther, 2007; 42: 130 – 5

[2] Adu et al. Influence of methanol fruit and leaf extract of Myristica fragrans on activity of some antibiotics. Afr J of Microbiol Res, 2014; 8: 1982 – 1986