Antimicrobial and antioxidant activities of Duboscia viridiflora and Brachyachne obtusiflora

Duboscia viridiflora (Family: Malvaceae) and Brachyachne obtusiflora (Family: Poaceae) are plants commonly found in west Africa. Leaves and stem bark of D. viridiflora as well as the leaves of B. obtusiflora are used to treat wounds and wound infections in Ghana [1]. Therefore the study sought to determine the antimicrobial and antioxidant activities of D. viridiflora and B. obtusiflora.

Preliminary phytochemical screening was performed on the methanol leaf (DVLE) and stem bark (DVSE) extracts of D. viridiflora and methanol leaf extract of B. obtusiflora (BOLE) to determine the secondary metabolites [2]. Micro broth dilution method was used to determine antimicrobial activity of DVLE, DVSE and BOLE [3]. Antioxidant activities of the DVLE, DVSE and BOLE were determined using 1,1-diphenyl-2-picryl hyrdazyl [4].

MIC of DVSE was 3.13 mg/mL against test organisms. MIC of DVLE against B. subtilis, E. coli, and P. aeruginosa was 12.5, 25.0 and 25.0 mg/mL, respectively. MIC of BOLEs against B. subtilis, E. coli, S. pyogenes and P. aeruginosa were 10.0, 20.0, 20.0 and 10.0 mg/mL, respectively (Table 1). DVLE, DVSE and BOLE exhibited antioxidant activity with IC₅₀ of 17.0 ± 0.006, 34.0 ± 0.004 and 127.0 ± 0.059 µg/mL, respectively. Tannins, flavonoids and glycosides were present in DVLE, DVSE and BOLE. Saponins were present in DVLE and DVSE but not BOLE.

DVLE, DVSE and BOLE possess antimicrobial and antioxidant activities.

Tab. 1: MICs of DVSE, DVLE and BOLE

Test organisms	MIC(mg/mL)
	DVSE	DVLE	BOLE
B. subtilis NTCC 10073	3.13	12.50	10.00
E. coli ATCC 25922	3.13	25.00	20.00
S. pyogenes (clinical strain)	nd	nd	20.00
P. aeruginosa ATCC 4833	3.13	25.00	10.00
nd: not determined

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

[2] Evans, WC. Trease and Evans Pharmacognosy 16th edition. Williams & Wilkins, Baltimore; 2009:1788

[3] Wiengand et al., Nat. Protoc 2008;3:163 – 175

[4] Chizzola et al., J. Agric Food Chem 2008;56:6897 – 6904