Isolation And Characterisation Of Bioactive Principles From Raphia Africana (otedoh)

Raphia africana (Otedoh) is a member of the palm family Arecaceae. The plant wascollected from banks of the creeks Ukoko and Uertsor in Buruku Local Government Areaof Benue State. The fruit mesocarp was extracted and subjected to phytochemical andantimicrobial screenings. The ethyl acetate extracts, obtained via different extractionprotocols (soxhlet extraction, microwave assisted extraction and maceration) weresubjected to Artemia salina lethality assay. Extracts (ethyl acetate and methanol) weresubjected to Gas Chromatography Mass Spectrometry (GCMS) and High-PerformanceLiquid Chromatography (HPLC) as part of pre-isolation analysis. Phytochemicalscreening showed the presence of steroids, triterpenes, alkaloids, anthroquinones, cardiacglycosides and flavonoids. Antimicrobial screening of the extracts showed the ethylacetate extract to have the broadest and highest activity against the test microbes, havinglower minimum inhibitory concentration (0.625 mg/mL) and a wider zone of inhibitiondiameter (27 mm) on Klebsiella pneumoniae. The ethyl acetate extract also showed goodminimum bactericidal/fungicidal concentration values on Staphylococcus aureus (2.5mg/mL), Klebsiella pneumoniae (1.25 mg/mL) and Candida albicans (2.5 mg/mL). Thehexane extract was the least active against the test microbes with chloroform andmethanol extracts showing intermediate activity. Extracts obtained by soxhlet extractionand microwave assisted extraction showed toxicity at a concentration of 269.2 mg/mL,while the extract obtained through maceration showed the lowest toxicity (467.7 mg/mL).The GCMS profiles showed the extracts to consist of lipids and diterpene alcohols whilethe selectively targeted HPLC showed traces of sterols (campesterol, cholestanol,cholesterol, ß-sitosterol, stigmasterol and tocopherol) and flavonoids (isovitexin, kaempferol and orientin). Crude extracts were extensively purified using vacuum liquidchromatography (VLC) and gel filtration (GF). Fractions from VLC and GF sessionswere characterised using Nuclear Magnetic Resonance Spectroscopy (NMR) and foundto be mainly lipids. Extensive chromatography allowed the isolation of saturated fattyacids (margaric and myristic acids), a monounsaturated fatty acid methyl ester (methyloleate), triglycerides, a sterol methyl ether, tentatively identified diosgenin-type steroidalsaponins, tentatively identified monogalactosyl diacylglycerides, monoacyl glyceridesand diacylglycerides. This is the first time these substances have been identified in themesocarp of this plant. The isolated compounds were tested against microbes and theyshowed higher but similar activity compared to the crude extracts. Ja 83 (amonogalactosyldiacylglyceride) showed the largest zone of inhibition againstStaphylococcus aureus (30 mm), against Klebsiella pneumoniae (31 mm) and 32 mmagainst Shigella dysenteriae while showing the least zone against Microsporum sp.Isolated compounds were inactive towards Aspergillus fumigatus and Aspergillus niger.Relatively mild behaviour of the crude extracts against Artemia salina, and the lipidicnature of the phytoconstituents reaffirm its use as a food source and it is recommendedthat this, now increasingly neglected tropical fruit tree, be actively cultivated for humanuse provided the toxicity studies allow them for such purpose.

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