Analysis of secondary metabolites and in vitro evaluation of extracts of Carica papaya and Azadirachta indica leaves on selected human pathogens

Abstract

Extraction of the leaves of Carica papaya (family Caricaceae) and Azadirachta indica (family Meliacea) were done using solvents with varying polarities (acetone, hexane and ethylacetate). The crude extracts were screened for phytoconstituents using the preliminary method and high-performance liquid chromatography (HPLC) for separation and quantification of the constituents. Susceptibility of three medically important microorganisms (Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922 and Candida alblicans) to the solvent extracts was tested at 100 mg/mL, 50 mg/mL and 25 mg/mL concentrations the disc diffusion technique. Tannins, saponins, alkaloids, steroids, flavonoids and anthraquinone were present in all the solvent extracts of A. indica and C. papaya. Protein was present in all the solvent extracts of A. indica but absent in all the solvent extracts of C. papaya. Terpenoid was only present in hexane extract of A. indica but absent in other solvent extracts of A. indica and C. papaya. Flavonoid was present in all but only absent in ethylacetate extract of A. indica. Glycoside was present in all but absent in hexane extract of A. indica. Coumarin was only present in acetone extracts of both plants and absent in other solvent extracts of the two plants. Extracts of Carica papaya and Azadirachta indica displayed varying inhibitory activities (between 5.00-15.00 mm) against the organisms at all the tested concentrations. Acetone extract of A. indica produced zones of inhibition ranging from 5.00-14.00 mm while acetone extract of C. papaya produces a range of 4.00-10.00 mm. Also, hexane extract of A. indica produced inhibition range of 7.00-10.00 mm whereas hexane extract of C. papaya produces a range of 5.00-15.00 mm. However, ethylacetate extract of A. indica produced inhibition range of 5.00-13.67 mm, while ethylacetate extract of C. papaya produce a range of 5.00-15.00 mm. Different compounds quantified as different peaks by HPLC in the different solvent extracts of Carica papaya are acacic acid, genistein, protodioscin, betulinic acid, phorbolester, creptolepinone, brusatol and alpha ionone while the fractions from the solvent extracts of Azadirachta indica are myricetin, azadirachtol, azadirachtin a, pentadecane, phytol, azadirachnol, quercetin, b caryophyllen, alpha ionone, ascaridole, trams.b.farnes. Results obtained in this work indicated that all the solvent extracts of Carica papaya and Azadirachta indica contained active phytoconstituents and the extracts displayed good potentials at preventing diseases associated with the microorganisms tested in this work.