Individual and Combined Antibacterial Activity of Crude Extracts from Medicinal Plants Carissa spinarum Linn and Carica papaya Linn.

Aim: To assess inhibitory effect of extracts, alone and in combination, from Carissa spinarum Linn (C. spinarum L.) and Carica papaya Linn (C. papaya L.) on Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The combined extracts used were C. papaya L leaves petroleum ether extract/C. spinarum L root methanolic extract (CPLP/CSRM), C. spinarum L leaves petroleum ether extract/C. papaya L seed ethanolic extract (CSLP/CPSE), C. spinarum L root ethanolic extract/C. papaya L leaves ethanolic extract (CSRE/CPLE), C. papaya L root ethanolic extract/C. spinarum L bark ethanolic extract (CPRE/CSBE) and C. papaya L leaves methanolic extract/C. spinarum L leaves methanolic extract (CPLM/CSLM). Study Design: In vitro antibacterial assay. Place and Duration of Study: Samples were collected from Samunge village at Loliondo in Ngorongoro district located in northern Tanzania. Antimicrobial bioassay was carried out at the Department of Molecular Biology and Biotechnology, University of Dar-es- Salaam, between March 2013 and June 2013. Methodology: The broth micro dilution method was used to determine minimum inhibition concentration (MIC). Fractional inhibitory concentrations were calculated from MICs of individual and combined extracts to determine interactions. Results: Plant extracts demonstrated MICs ranging from 312 to 5000 μg/ml. The combination of plant extracts against S. aureus resulted into antibacterial activity of CPSE, CPRE, CPLM, CSLM and CPLP extracts to increase by 4-, 2-, 4-, 4-, and 2-fold, respectively. Activity of CSLP, CPLM and CSLM increased by 2-fold against E. coli. Synergy was demonstrated by CPLM/CSLM against S. aureus. Some combinations were additive including CPRE/CSBE, CPLP/CSRM and CSLP/CPSE against S. aureus and CSLP/CPSE, CPRE/CSBE, CPLM/CSLM against E. coli. Nevertheless, antagonism was demonstrated by CSRE/CPLE, CPLP/CSRM against E. coli and CSLP/CPSE and CSRE/CPLE against S. aureus. Conclusion: This study revealed the importance of using plant-based antibacterial agents in combined therapy to increase efficacy. Extracts of C. spinarum L and C. papaya L could be a source of antibacterial agents when utilized in combination therapy for patients with severe E. coli and staphylococcal infections. These predictors, however, need to be validated to improve their quality.

Analysis of Phytochemical and Antibacterial Activity of Carissa spinarum Linn Crude Extracts.

Aims: To screen for the antibacterial activity of Carissa spinarum L. crude extracts against Escherichia coli and Staphylococcus aureus. The phytochemicals that are responsible for the bioactivity were also screened. Study Design: In vitro assay of antibacterial properties. Place and Duration of Study: Samples were collected from Samunge village at Loliondo in Ngorongoro district located in northern Tanzania. Extraction and phytochemical analyses were conducted at the Department of Traditional Medicine of the National Institute of Medical Research (NIMR) in Dar-es-Salaam, Tanzania. Antimicrobial bioassay was carried out at Department of Molecular Biology and Biotechnology at the University of Dar-es-Salaam between March 2013 and June 2013. Methodology: Disk diffusion test was used to determine antimicrobial activity of the plant extracts. Chemical tests were used to determine the group of phytochemicals present in the sample extracts. Results: Sensitivity testing results indicated that S. aureus was found to be more sensitive than E. coli. Carissa spinarum L. methanolic extracts were the most active constituents and demonstrated the zone of inhibition values of 11.66±0.42 mm and 13.33±1.53 mm in diameter against E. coli and S. aureus, respectively. The highest percentage values of relative inhibition zone diameter of 57.24% (E. coli) and 70.17% (S. aureus) were demonstrated by C. spinarum L. root methanolic extracts. In contrast, C. spinarum L. bark extracts did not show any antibacterial activity against the two bacterial species. Plant extracts demonstrated the minimum inhibitory concentrations ranging from 312 to 5000 μg/ml. Phytochemical screening of crude extracts revealed the presence of saponins, alkaloids, flavonoids, tannins and sterols. The presence of these phytochemicals in the extracts was linked with observed antibacterial activity. Conclusion: This study has revealed that the antibacterial activity of different extracts of C. spinarum L. was attributed to the presence of several phytochemicals. The study findings suggest likelihood of designing and developing potentially active antibacterial agents from C. spinarum L.