Crude extracts of, and purified compounds from,Pterocarpus angolensis, and the essential oil ofLippia javanica: their in-vitro cytotoxicities and activities against selected bacteria andEntamoeba histolytica

Abstract

In a recent study, various extracts of Pterocarpus angolensis were prepared and tested against bacteria. The acetone extract was found to be the most active against all the bacteria investigated, with minimum inhibitory concentrations varying from 0.0156 mg/ml against Staphylococcus aureus to 2 mg/ml against Enterobacter cloacae. Seven pure compounds were subsequently isolated from the ethanol extract of P. angolensis. Using several chromatographic and spectroscopic methods, the structures of five of these compounds - phthalate and four derivatives of epicatechin [(-)-epicatechin, epicatechin-3-O-galate, epicatechin (4beta-8)-epicatechin (B2), and a hexamer of epicatechin] - were successfully determined. The seven purified compounds were then further tested, in vitro, against Staphylococcus aureus and Entamoeba histolytica, and for their in-vitro cytotoxic activity. Although all seven were active against S. aureus, just one of the purified compounds from P. angolensis and piperitenone, a pure compound isolated from Lippia javanica essential oil, were found to have marked activity against Entamoeba histolytica, with median inhibitory concentrations (IC(50)) of 25 and 100 microg/ml, respectively. The other P. angolensis compounds were either weakly active or showed no activity against the amoebae when tested at concentrations up to 400 microg/ml. All seven compounds isolated from P. angolensis showed less toxicity against cultures of human (HCT-8) cells than piperitenone, with IC(50) of 175-375 microg/ml. The presence of epichatechin and derivatives (with strong antibacterial activities but generally weak activities against Entamoeba histolytica) in the stem bark of P. angolensis has thus been demonstrated. Further investigation of the activities of these compounds and their potential use in the treatment of bacterial diseases appears justified.

Antimicrobial and Phytochemical Screening of some Zimbabwean Medicinal Plants

“…A. niger was insensitive to most of the plant extracts with two, only showing an MIC=2.5 mg/ml. These results tend to be supported by similar findings by other reporters 2,3,[8][9][10][11]14,17,20 . In general, the results however, show greater activity by the root extract over the leaf, fruit or stem bark extract.…”

Woody species from the Mozambican Miombo woodlands: A review on their ethnomedicinal uses and pharmacological potential

“…to treat diarrhea, heavy menstruation, nose bleeding, headache, stomach-ache, parasitic worms, sores and skin problems (Takawira-Nyenya, 2005). Pharmacological studies on P. angolensis revealed antibacterial activity of seeds (Steenkamp et al, 2004), stem bark, roots and leaf extracts (Luseba et al, 2007;Mulaudzi et al, 2011;Samie et al, 2009) and antifungal activity of leaf and bark extracts (Mulaudzi et al, 2011). The latter also showed HIV-1 reverse transcriptase inhibitory activity (Mulaudzi et al, 2011) as well as anthelmintic effects (McGaw et al, 2007;Molgaard et al, 2001).…”

“…Anti-inflammatory activity was also detected in stem bark extracts . Samie et al (2009) demonstrated the presence of epichatechin and derivatives (with strong antibacterial activities but generally weak activities against Entamoeba histolytica) in stem barks.…”

Biodiversity Studies in Key Species from the African Mopane and Miombo Woodlands

“…For example, the bark is used as a powerful astringent to treat diarrhea, heavy menstruation, nosebleeding, headache, stomachache, schistosomiasis, sores, and skin problems; the root is believed to cure malaria, blackwater fever and gonorrhea [6,24,28,35,36]. Research studies reveal promising results concerning their antibacterial [37][38][39], antifungal [38], anthelmintic [40,41], and HIV-1 reverse transcriptase inhibitory properties [38] ( Table 1). At the environmental level P. angolensis is able to establish nitrogen-ixing symbiosis with rhizobium bacteria and therefore relevant for soil fertilization.…”

“…Pterocarpus angolensis DC Antischistosomal [90] RAPD [79,80] Stem, stem bark, leaves: anthelmintic [40] Seeds: antibacterial [91] Stem bark: antibacterial and anti-inlammatory; lack of mutagenicity [92] Stem bark, leaves: anthelmintic, antibacterial, and cytotoxic [41] Antibacterial [93] Stem bark: antibacterial; epicatechin and derivatives identiied [37] Stem bark: antibacterial; leaves, stem bark: antifungal, HIV-1 reverse transcriptase inhibitory [38] Leaves, stem bark: anti-inlammatory [94] Stem bark, roots: antibacterial; tannins and saponins identiied [39] Colophospermum mopane (Benth. )…”