Antimicrobial and antioxidant activities of geraniin and aqueous leaf extract of Phyllanthus muellerianus (Kuntze) Exell.

Introduction:

Phyllanthus muelllerianus (Kuntze) Exell. (Family Euphorbiaceae) is used in African ethnomedicine for treatment of microbial infections and wounds [1]. The aim of the study was to determine antimicrobial and antioxidant properties of aqueous leaf extract (ALE) of P. muellerianus and its isolate, geraniin [2].

Method:

Agar diffusion and broth micro-dilution methods were used to determine the antimicrobial activity of ALE and geraniin against Gram-positive bacteria (Staphlococcus aureus, ATCC 25923, Bacillus subtilis, NCTC 10073 and clinical strain of Streptococcus pyogenes), Gram-negative bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853) and fungal strain (Candida albicans). Free radical scavenging activities of ALE and geraniin was determined using DPPH method.

Results:

ALE and geraniin were active against all test microbes with MIC range of 0.08 – 5.0 mg/mL and MBC range of 1.25 – 50 mg/mL (Table 1). The time kill kinetics of geraniin and ALE indicate that mode of action as static within concentration range considered. Antioxidant activities (IC₅₀) of ALE, geraniin and α-tocopherol were 0.123, 1.85 and 0.034 µg/mL respectively. Phytochemical screening of ALE revealed the presence of alkaloids, glycosides, saponins, tannins, flavonoids and terpenoids.

Tab. 1: MIC and MBC of aqueous extract of P. muellerianus, geraniin and reference drugs (ciprofloxacin and ketoconazole), nd: not determined

Test organisms	P. muellerianus		Geraniin		Ciprofloxacin MIC (µg/mL)	Ketoconazole MIC/(µg/mL)
	MIC (mg/mL)	MBC (mg/mL)	MIC (mg/mL)	MBC (mg/mL)
B. subtilis	1.25	20.00	0.31	5.00	0.10	nd
E. coli	5.00	50.0	1.25	10.00	0.13	nd
P. aeruginosa	0.31	10.00	0.08	2.50	0.25	nd
S. aureus	0.31	5.00	0.16	1.25	0.25	nd
S. pyogenes	0.63	10.00	0.08	2.50	0.10	nd
C. albicans	0.50	5.00	0.16	5.00	nd	5.00

Conclusion:

ALE and geraniin possess antimicrobial and antioxidant properties.

References:

[1] Agyare et al. (2009), J. Ethnopharmacol, 125:393 – 403.

[2] Agyare et al. (2011), Phytomedicine,18(6):617 – 24.