Antibacterial Activity of Flavonoids againstStaphylococcus epidermidis, a Skin Bacterium

Bioactive Compounds from Microalgae Spirulina platensis as Antibacterial Candidates Against Pathogen Bacteria

Microbial infection by bacteria has caused severe health problems worldwide. Treatment with antibiotics as the current solution has several drawbacks and triggers the phenomenon of bacterial resistance. Therefore, there is an urgency to look for a natural antimicrobial that is safer and has fewer side effects. One of the most promising antibacterial agents is Spirulina platensis. This research was conducted to evaluate the antibacterial activity of microalgae S. platensis against Propionibacterium acne, Staphylococcus epidermidis, and Enterobacter aerogenes and identify compounds from the active fraction of microalgae. Biomass was extracted with ethanol 96% using the reflux method then partitioned with immiscible solvents such as hexane, ethyl acetate, and water. Partial purification was carried out by chromatography techniques such as thin-layer chromatography and column chromatography. The compounds of active fractions were identified by GC-MS analysis. The result showed that ethyl acetate extract had vigorous antibacterial activity against all tested bacteria. The highest activity (14.4 ± 0.63 mm and 16.9 ± 1.48 mm) was achieved against P. acne; followed by S. epidermidis (13.05± 0.14 mm and 13.15 ± 0.0 mm), and E. aerogenes (11.7 ± 2.05 mm and 12.6 ± 1.90 mm), at concentrations 20,000 ppm and 30,000 ppm, respectively. The results indicated that the extract is more sensitive to Gram-positive bacteria (P. acne and S. epidermidis) than Gram-negative bacteria (E. aerogenes). Purification of the extract resulted in fraction 2 and fraction 6 as the most potential fractions for further analysis and identification. Based on the antibacterial activity, inhibition zones of fractions are wider than extracts. It could be assumed that the purification process enhances the activity of a sample. GC-MS analysis revealed that the dominant compounds of fractions 2 and 6 were bis (2-ethylhexyl) phthalate (67.76%) and 1,2-Benzendicarboxilic acid, bis (2-ethylhexyl) ester (50,88%), respectively. This result indicated that the ethyl acetate fraction of the microalgae S. platensis has the potential as a natural antibacterial.

Chemical structures and hepatoprotective effects of constituents from Cassia auriculata leaves

An 80% aqueous acetone extract of Cassia auriculata leaves was found to show a protective effect on D-galactosamine-induced cytotoxicity in primary cultured mouse hepatocytes. From the 80% aqueous acetone extract, we isolated a new benzocoumarin glycoside, avaraoside I (1), and a new flavanol dimer, avaraol I (2), together with 29 known constituents. The structures of the new compounds were elucidated on the basis of chemical and physicochemical evidence. In addition, three isolated compounds, pseudosemiglabrin (15, 0.0011%), (2S)-7,4'-dihydroxyflavan(4β→8)-catechin (22, 0.00075%), and (2S)-7,4'-dihydroxyflavan(4β→8)-gallocatechin (23, 0.092%), displayed hepatoprotective effects equivalent to that of the hepatoprotective agent, silybin.

Antibacterial activity in spices and local medicinal plants against clinical isolates of Karachi, Pakistan

CONTEXT

Development of resistance in human pathogens against conventional antibiotic necessitates searching indigenous medicinal plants having antibacterial property. Twenty-seven medicinal plants used actively in folklore, ayurvedic and traditional system of medicine were selected for the evaluation of their antimicrobial activity for this study. Eleven plants chosen from these 27 are used as spices in local cuisine.

OBJECTIVE

Evaluation of the effectiveness of some medicinal plant extracts against clinical isolates.

MATERIAL AND METHODS

Nonedible plant parts were extracted with methanol and evaporated in vacuo to obtain residue. Powdered edible parts were boiled three times and cooled in sterile distilled water for 2 min each and filtrate collected. The minimum inhibitory concentration (MIC) of plant extracts and filtrates/antibiotics was evaluated against clinical isolates by microbroth dilution method.

RESULTS

Water extract of Syzygium aromaticum L. (Myrtaceae) buds, methanol extracts of Ficus carica L. (Moraceae) and Olea europaea L. (Oleaceae) leaves and Peganum harmala L. (Nitrariaceae) seeds had MIC ranges of 31.25-250 µg/ml. S. aromaticum inhibited growth of Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Salmonella enterica serovar Typhi and Pseudomonas aeruginosa. F. carica and O. europaea inhibited growth of S. aureus, S. epidermidis, and S. pyogenes whereas P. harmala was effective against S. aureus, Acinetobacter calcoaceticus and Candida albicans. Ampicillin, velosef, sulfamethoxazole, tetracycline and ceftazidime, cefotaxime, cefepime, which are used as control, had MIC ≥ 50 and 1.5 µg/ml, respectively, for organisms sensitive to extracts.

DISCUSSION AND CONCLUSION

Mono/multiextract from identified plants will provide an array of safe antimicrobial agents to control infections by drug-resistant bacteria.