PHYTOCHEMICAL SCREENING AND IN VITRO ANTILISTERIAL ATTRIBUTES OF DIFFERENT AQUEOUS AND ETHANOLIC LEAF EXTRACTS

Introduction. Listeria monocytogenes represents the Listeria species most commonly associated with disease in humans. The majority (99%) of the infections caused by L. monocytogenes are food-borne being ingestion of contaminated food especially contaminated ready-to-eat food products that do not undergo subsequent reheating. This organism has great economical implications in the food industry due to recalls of contaminated food products and temporary shutdown of many food processing plants. There has been lots of interest recently in the role of complementary and alternative medicines for the treatment of various acute and chronic diseases. The revival of interest in the use of African medicinal plants by many developing countries and the World Health Organization (WHO) has led to intensified efforts to explore the numerous plants with medicinal importance. A large number of phytochemicals belonging to several chemical classes have been shown to have inhibitory effects on all types of microorganisms in vitro. Knowledge of the chemical constituents of plants and their anti-Listeria ability is desirable because such information will be value for synthesis of complex chemical substances. The aim of this work was to study the phytochemical qualitative profiles and in vitro antilisterial attributes of aqueous and ethanolic  leaf extracts from several plants against  earlier  documented Ready To Eat (RTE)  associated multi antibiotic resistant L. monocytogenes strains.  Materials and Methods. The examined aqueous and ethanolic leaf extracts were derived from Psidium guajava (guava),  Zingiber officinale (Ginger), Dacryodes edulis (African pear), Citrus aurantifolia (Lime), Funtumia elastica (silkrubber), Vernonia amygdalina (Bitter leaf), Cassia alata and  Moringa oleifera (horseradish tree). The respective L. monocytogenes strains utilized were; LMSN 70, LMEW 94 and LMMP 104. Invitro assay of aqeous and ethanol estracts of plants was assayed by agar well diffusion assay. Results and discussion. Alkaloids, saponins, steroids, terpenoids, cardiac glycoside, reducing sugar, phenolics, resins, flavonoids, and tannins  were detected in Z. officinale ethanolic leaf extract  whilst cardiac glycoside was absent in  ethanolic leaf extracts of D.  edulis, C. aurantifolia and F.  elastica.  Alkaloids, saponins, steroids, terpenoids, cardiac glycoside, reducing sugar, phenolics, resins, flavonoids, and tannins  were detected in crude aqueous leaf extracts of Z.  officinale and  M.  oleifera.F. elastica ethanolic leaf extract displayed the highest antilisterial potential at the least concentration; 100mg/ml whilst amongst the aqueous extracts, V.  amygdalina leaf extract exhibited maximal antilisterial activities  comparable with antilisterial inhibitory growth zones elicited by the  respective ethanolic  extracts with the exception of   M.  oleifera extracts. Conclusion.  Further studies aimed at the fractionation of the respective crude  extracts especially F.  elastica and exposing the respective multi antibiotic resistant food borne L. monocytogenes strains to these fractionated leaf  extracts should be conducted.