The antibacterial effect of selected medicinal plant extracts against multi-drug resistance staphylococcus aureus (MRSA) using 2 dimensional electrophoresis (2-DE)

Abstract

Plant parts from 15 species were collected for anti-MRSA screening. Crude extraction was carried out using ethanol and water. The yield of the ethanol extracts ranged from 5.2% (w/w) to 38% (w/w) while for water soluble extracts, the yield ranged from 4.5% (w/w) to 26.7% (w/w). The screenings for anti-MRSA activity were performed in 96-well microtiter plate using micro broth dilution method. The reference strain used was ATCC33591, and Vancomycin was used as the positive control. Out of 30 crude extracts which were screened for anti-MRSA activity, 17 extracts were found to be active. The MIC and MBC level obtained was as low as 0.3 4g/4L for 3 crude extracts, namely the ethanol extract of Macaranga gigantea, and both ethanol and water soluble extracts of Quercus infectoria. These 3 extracts were screened for the presence of major heavy metal elements: Mercury (Hg), Lead (Pb), Arsenic (As) and Cadmium (Cd). These elements were the most common major heavy metal elements screened in herbal products in the market. The water soluble extract of Q. infectoria and the ethanol extract of M. gigantea passed the permissible level according to Malaysia Poison Act 1952. These 2 extracts were tested for animal toxicity by administration to mice and were evaluated at oral gavage dosages of 0, 10, 200, 1000, 2000 and 5000 mg/kg bodyweight. From this test, the water soluble extract of Q. infectoria showed 0% mortality for all dosages. For ethanol extract of M. gigantea, death of mice were first seen at dose of 2000 mg/kg bodyweight with 10% mortality and followed by 30% mortality of mice in dose of 5000 mg/kg bodyweight. No death in mice was observed in lower level of dosages. However, median lethal dose (LD50) for ethanol extract of M. gigantea is higher than 5000 mg/kg bodyweight. Based on it being not toxic to mice and the MIC obtained, the water soluble extract of Q. infectoria was selected for general profiling by HPLC for a general chemical fingerprint. Then, 2D PAGE profiling of treated and non-treated MRSA with the water soluble extract of Q. infectoria were performed to investigate any differences of protein expression. By using the pI 3-10 gel setting, 2D-PAGE gel images obtained detected some 157 protein spots in non-treated MRSA while there were only 13 protein spots detected in treated MRSA. This finding also reveals the potential use of proteomics in-vitro in the evaluation of the response to anti-MRSA agent in terms of quantification of protein expression after the treatment. This study also suggests that the water soluble extract of Q. infectoria is a potential anti-MRSA candidate to be explored further for antibiotic development in the future.