Some Medicinal Benefits of Psidium Guajava (Guava) and Portulaca oleracea
Table (3): Free radical scavenging activities of two tested medicinal plants
A concentration-dependent scavenging activity was clearly demonstrated. At 100µl, the inhibition percent of Me-OH, extracts was determined as 90.27% and 56.52% in Psidium Guajava (Guava) and Portulaca oleracea, respectively. These results indicated that Me-OH extract of Psidium Guajava (Guava) exhibited the highest DPPH radical scavenging activity compared to Portulaca oleracea. The highest DPPH radical scavenging activity of Psidium Guajava (Guava) seems to be attributed to the high concentration of phenolic compounds in this extracts, which could be the electron donors, and hence can react with free radicals to convert them to more stable products and terminate radical chain reaction, that could make this herb contains exploitable antioxidant activities; this finding is in a full agreement with that obtained by  and .
Results of the Antimicrobial activity is presented in Table 4. As shown from the table,
Both plants, showed different antibacterial behavior against the targeted organisms; Psidium Guajava (Guava) showed moderate effect (++) against all Gram +ve organisms (Staphylococcus aureus, Bacillus subtilis and Listeria monocytogenes), also it showed the same effect against Aspergillus niger (Fungus) and Candida albicans (Yeast); on the other hand Psidium Guajava (Guava) showed weak effect against Gram –ve organisms (E.coli, Pseudomonas aeruginosa and Salmonella typhi).
Antimicrobial activities of Psidium Guajava (Guava), and Portulaca oleracea
* Antimicrobial activities were expressed as inhibition diameter zones in millimeters (mm) : - (negative) = 0 mm; + (weak) =1-4 mm’ ++ (moderate) = 5-10 mm; +++ (strong) = 10-15 mm; and ++++ (very strong) ≥ 16 mm.
** Microorganisms used were S. aureus (ATCC 25923), B. subtilis (ATCC 6633), L. monocytogenes (ATCC 7644), E.coli (ATCC 35218), P. aeruginosa (ATCC 9027), S. typhi (ATCC 14028, A. niger (ATCC 1957) and C. albicans (ATCC 10231).
Portulaca oleracea showed very strong effect against all tested organisms except Gram-ve organisms (Staphylococcus aureus, Bacillus subtilis, Listeria monocytogenes, Aspergillus niger and Candida albicans), while it showed only moderate effect against Gram –ve organisms (E.coli, Pseudomonas aeruginosa and Salmonella typhi). This results revealed that both plant extracts were effectively killed all tested microorganisms; this is in agreement with the same results proposed by .
The findings of this study support the view that some medicinal plants are promising sources of potent antioxidants and may be efficient as preventive agents in the pathogenesis of some diseases. It can also be used in stabilizing food against oxidative deterioration. Psidium Guajava (Guava) and Portulaca oleracea, which contain the highest amount of flavonoid and phenolic compounds, exhibited the greatest antioxidant activity, are two of these medicinal plants that showed greater antimicrobial activity against all tested microorganisms, however, this study should follow by extensive phytochemical and pharmacological studies on plants used in this study.