In the present investigation, the active components which are the secondary metabolite of Calotropis procera was studied. Column chromatography and thin layer chromatography and antibacterial screening leaf extract of equeous, methanol, n.hexane and ethanol were used to extract the plant for crude extracts. Fractionated pure isolates obtained from column chromatography using different solvent ratio and the crude extracts were tested against some selected pathogenes, microorganisms such as P. aeruginosa, S. typhi, S. aureus and B. subtile.
Two hundred and fifty (250) gram of the pulverized dried was weighed for each solvent extraction and 28.50 ± 1.00, 12.30 ± 1.00, 16.40 ± 1.0 (g) and 22.60 ± 1.00 respectively with correspondence weigh of fractionated pure isolates of the extract obtained from column chromatography of 13.00 ± 1.00, 7.20 ± 1.00, 8.80 ± 1.00 and 10.30 ± 1.00 (ml) was obtained (Table 1).
Table (2) showed results of phytochemical analysis which revealed that saponins, tannins, alkaloids, flavonoids and cardiac glycoside were present in n.hexane extracts whereas reducing sugar, steroids, anthroquinone, terpenoids phenol and phlobatannins were absent in n.hexane plant extracts. Methanolic extracts showed the highest active components of tannins, saponins, alkaloids, flavonoids, cardiac glycoside and terpenoids in methanolic extracts whereas reducing sugar, phenol, and phlobatannins were absent. Ethanolic extracts showed the presence of saponins, tannins, alkaloids, flavonoids, terpenoids and cardiac glycoside whereas reducing sugar, steroids, anthroquinone, phenol and phlobatannins were absent. Similarly, in aqueous extracts, saponins, tannins, alkaloids and terpenoid were present whereas reducing sugar, steroids, flavonoids, terpenoids, phenol and cardiac glycoside were absent. This result agreed with Peni et al. (2010).
Table 3 showed antibacterial activity of crude extracts against test organisms. The nhexane crude extract showed zone diameter of inhibition of 6.00 ± 2.00 on B. subtile, 9.33 ± 0.00, 13.02 ± 0.00, 20.00 ± 0.00 and 29.70 ± 0.00 on S. typhi, 0.60 ± 0.00, 5.60 ± 0.00, 14.00 ± 1.00 and 18.10 ± 0.00 on S. aureus, 7.60 ± 0.00, 10.60 ± 0.00, 11.00 ± 1.00 and 21.10 ± 0.00 on P. aeruginosa at different concentration of 62.5, 125 mg/ml, 250 mg/ml and 500 mg/ml. Result of methanolic crude extracts showed the mean zone diameter of inhibition of 7.60 ± 0.00, 14.00 ± 0.00 and 19.00 ± 0.00 on B. subtilis, 10.50 ± 0.00, 16.22 ± 0.00, 25.00 ± 1.00 and 33.80 ± 0.00 on S. typhi, 2.20 ± 1.00, 4.80 ± 1.00, 9.20 ± 0.00 and 14.70 ± 0.00 on S. aureus, 1.20 ± 1.00, 9.80 ± 1.00, 9.20 ± 0.00 and 14.70 ± 0.00 on P. aeruginosa. Result of ethanolic crude extracts showed the mean zone diameter of inhibition of 16.10 ± 0.00, 18.00 ± 1.00, 15.10 ± 0.00 and 15.30 ± 0.00 on B. subtilis, 18.0 ± 1.00, 20.50 ± 1.00 and 25.10 ± 1.00 on S. typhi, 2.10 ± 1.20, 10.20 ± 1.00, 13.20 ± 0.00 and 22.30 ± 0.00 on S. aureus; 2.0 ± 1.20, 11.2 ± 1.00, 17.30 ± 0.00 and 22.30 ± 0.00 on P. aeruginosa. Result of aqueous crude extracts showed the mean zone diameter of inhibition of 0.00 ± 0.00, 0.00 ± 0.00, 17.20 ± 0.11and 20.30 ± 4.00 on B. subtilis, 12.00 ± 0.00, 20.00 ± 0.00, 22.30 ± 1.00 and 28.80 ± 0.20 on S. typhi; 9.00 ± 0.00, 13.00 ± 0.00, 18.30 ± 1.00 and 31.00 ± 0.00 on S. aureus; 9.00 ± 0.00, 12.00 ± 0.00, 21.30 ± 1.00 and 31.00 ± 0.00 on P. aeruginosa. The methanolic extracts were observed to be more potent than other extracts on the test bacteria with the mean zone diameter of inhibition of 25.00 ± 0.00 and 33.80 ± 0.00 at the concentration of 500mg/ml on S. typhi.
From Table 4, fractionated pure isolate of the extract showed highest zone diameter of inhibition of 27.50 ± 0.00 and 35.8 ± 0.00 at the concentration of 50 ml and 100 ml respectively on S typhi compared to the positive control range 34.00 ± 1.00 and 49.20 ± 1.00. The minimum bactericidal concentration (MBC) of crude and fractionated pure isolates showed effectiveness on both S. typhi and S. aureus at the concentration of 250mg/ml and 500 mg/lm, 50 ml and 100ml respectively. The above indication from agar well diffusion methods, the different crude extracts showed visible effect on crude extracts when compared to the fractionated pure isolates of the extracts and the positive control. This, confirming the assertion that different solvent extracts of same plant have different pharmacological properties. aqueous is the commonly used solvent by traditional healers to extract pharmacologically active compounds because of its easy availability (Shale et al., 1999).
The results Methicillin Resistant Staphylococcus Aureus Test (MRSA) showed a little longer time of declination in S. aureus within 12 h at the concentration of 250 mg/ml, 500mg/ml, 50 ml and 100ml of crude and fractionated pure extracts after an overnight incubation period. Hashim et al. (2017) reported a time-dependent decline in the case of S. aureus, with a 90% reduction achieved within 8 h of exposure to Cymbopogon schoenanthus essential oil of plant extract. From the results of the findings on MRSA, among the test organisms used, S. typhi revealed a very quick time of declination at the concentration of 250 mg/ml, 500 mg/ml, 50 ml, and 100 ml of crude and fractionated extracts within 4 h of the period of incubation. This was followed by a consistent reduction in the growth of S typi until a constant state of zones of inhibition was established as a benchmark. S. typhi showed less MRSA at concentrations compared to S. aureus that decline at 12 h which is an indication that the plant Calotropis procera leaf extracts has bacteriostatic effects on the test bacteria. Thus, the results deduced that fractionated pure isolate of the extracts were more significantly higher than the crude extracts at 0 < 0.5 level of significance compared to the positive control; this could be due to the synergism of the solvent. The finding therefore concludes that the plant Calotropis procera contains a potential source of bioactive compounds that can be used in management of typhoid fever and wound infections.