Investigation of antibacterial mechanism and identification of bacterial protein targets mediated by antibacterial medicinal plant extracts.

In this paper, we investigated the antibacterial mechanism and potential therapeutic targets of three antibacterial medicinal plants. Upon treatment with the plant extracts, bacterial proteins were extracted and resolved using denaturing gel electrophoresis. Differentially-expressed bacterial proteins were excised from the gels and subjected to sequence analysis by MALDI TOF-TOF mass spectrometry. From our study, seven differentially expressed bacterial proteins (triacylglycerol lipase, N-acetylmuramoyl-L-alanine amidase, flagellin, outer membrane protein A, stringent starvation protein A, 30S ribosomal protein s1 and 60 kDa chaperonin) were identified. Additionally, scanning electron microscope study indicated morphological damages induced on bacterial cell surfaces. To the best of our knowledge, this represents the first time these bacterial proteins are being reported, following treatments with the antibacterial plant extracts. Further studies in this direction could lead to the detailed understanding of their inhibition mechanism and discovery of target-specific antibacterial agents.

Antioxidant, Metal Chelating, Anti-glucosidase Activities and Phytochemical Analysis of Selected Tropical Medicinal Plants.

The purpose of this investigation was to determine the antioxidant potentials and anti-glucosidase activities of six tropical medicinal plants. The levels of phenolic constituents in these medicinal plants were also quantified and compared. Antioxidation potentials were determined colorimetrically for scavenging activities against DPPH and NO radicals. Metal chelating assay was based on the measurement of iron-ferrozine absorbance at 562 nm. Anti-diabetic potentials were measured by using α-glucosidase as target enzyme. Medicinal plants' total phenolic, total flavonoid and hydroxycinnamic acid contents were determined using spectrophotometric methods, by comparison to standard plots prepared using gallic acid, quercetin and caffeic acid standards, respectively. Radical scavenging and metal chelating activities were detected in all medicinal plants, in concentration-dependent manners. Among the six plants tested, C. nutans, C. formosana and H. diffusa were found to possess α-glucosidase inhibitory activities. Spectrophotometric analysis indicated that the total phenolic, total flavonoid and hydroxycinnamic acid contents ranged from 12.13-21.39 mg GAE per g of dry sample, 1.83-9.86 mg QE per g of dry sample, and 0.91-2.74 mg CAE per g of dry sample, respectively. Our results suggested that C. nutans and C. formosana could potentially be used for the isolation of potent antioxidants and anti-diabetic compounds. To the best of our knowledge, this study represents the first time that C. nutans (Acanthaceae family) was reported in literature with glucosidase inhibition activity.

Antibacterial, anti-glucosidase, and antioxidant activities of selected highland ferns of Malaysia.

BACKGROUND: Ferns contain natural products with potential therapeutic applications. Current knowledge of the pharmacological properties of ferns, specifically those growing at high altitudes, is limited. This study aimed to evaluate the phytochemical contents as well as antibacterial, anti-glucosidase, and antioxidant activities of four highland ferns in Malaysia. RESULTS: Aqueous extracts of the leaves and rhizomes of Cyathea latebrosa, Dicranopteris curranii, Gleichenia truncata, and Phymatopteris triloba were analysed. P. triloba leaf extract had the highest contents of total flavonoids (118.6 mg/g dry matter), hydroxycinnamic acids (69.7 mg/g dry matter), and proanthocyanidins (29.4 mg/g dry matter). P. triloba leaf and rhizome extracts as well as G. truncata leaf extract inhibited the growth of both Gram-positive and Gram-negative bacteria. P. triloba leaf extract produced a minimum inhibitory concentration (MIC) value of 0.78 mg dry matter/mL when tested against Pseudomonas aeruginosa, which is 2.5-fold higher than that of ampicillin. Among all extracts, P. triloba leaf extract had the highest anti-glucosidase activity (EC50 = 56 µg dry matter/mL) and also the highest antioxidant potential based on DPPH radical scavenging and Ferric Reducing Antioxidant Power assays. Antioxidant activities of both the leaf and rhizome extracts correlated positively with total flavonoid and hydroxycinnamic acid contents (R2 = 0.80-0.95). On the other hand, anti-glucosidase activity correlated with total proanthocyanidin contents in both the leaf and rhizome extracts (R2 = 0.62-0.84). CONCLUSIONS: In conclusion, highland ferns are potential sources of antibacterial agents, glucosidase inhibitors, and antioxidants.