Antibacterial activity of Dioscorea bulbifera Linn. extract and its active component flavanthrinin against skin-associated bacteria.

BACKGROUND: Dioscorea bulbifera Linn. has been used for wound care in Thailand. However, a comprehensive evaluation of its antibacterial activity is required. This study aimed to investigate the antibacterial efficacy of D. bulbifera extract against skin-associated bacteria and isolate and characterize its active antibacterial agent, flavanthrinin. METHODS: Air-dried bulbils of D. bulbifera were pulverised and extracted with hexane, dichloromethane, ethyl acetate, methanol, ethanol, and distilled water; vacuum filtered; concentrated; freeze-dried; and stored at -20 ºC. Antibacterial activity of the extracts was assessed using microdilution techniques against several skin-associated bacteria. Thin-layer chromatography (TLC) bioautography was used to identify the active compounds in the extract, which were fractionated by column chromatography and purified by preparative TLC. The chemical structures of the purified compounds were analysed using nuclear magnetic resonance (NMR). The cytotoxicity of the extract and its active compounds was evaluated in Vero cells. RESULTS: The ethyl acetate extract exhibited distinct inhibition zones against bacteria compared to other extracts. Therefore, the ethyl acetate extract of D. bulbifera in the ethyl acetate layer was used for subsequent analyses. D. bulbifera extract exhibited antibacterial activity, with minimum inhibitory concentrations (MICs) of 0.78-1.56 mg/mL. An active compound, identified through TLC-bioautography, demonstrated enhanced antibacterial activity, with MICs of 0.02-0.78 mg/mL. NMR analysis identified this bioactive compound as flavanthrinin. Both D. bulbifera extract and flavanthrinin-containing fraction demonstrated potent antibacterial activity against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), and S. epidermidis. The flavanthrinin containing fraction demonstrated low cytotoxicity against Vero cells, showing CC50 values of 0.41 ± 0.03 mg/mL. These values are lower than the MIC value, indicating that this fraction is safer than the initial ethyl acetate extract. CONCLUSIONS: Dioscorea bulbifera extract and its bioactive component flavanthrinin demonstrated significant antibacterial activity against the skin-associated bacteria Staphylococci, including MRSA. Flavanthrinin has potential as a complementary therapeutic agent for managing skin infections owing to its potent antibacterial effects and low cytotoxicity.

Variation in the Antibacterial and Antioxidant Activities of Essential Oils of Five New Eucalyptus urophylla S.T. Blake Clones in Thailand.

Eucalyptus oils are widely used for a variety of purposes. This study investigates the terpenoid compositions and antibacterial and antioxidant activities of eucalypt leaf oils extracted from four E. urophylla clones and one E. urophylla × E. camaldulensis hybrid clone grown in Thailand. According to GC/MS analysis, the E. urophylla oils were mainly composed of 1,8-cineole, α-terpinyl acetate, ß-caryophyllene, and spathulenol, while 1,8-cineole, α-terpinyl acetate, p-cymene, and γ-terpinene were mostly identified in the hybrid oil. All eucalypt oils exhibited a significant bacteriostatic effect against Gram-positive bacteria, Streptococcus pyogenes, Staphylococcus aureus, Listeria monocytogenes, and Bacillus cereus. Only the hybrid oil had an effect on all Gram-negative bacteria tested, including Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa, and Enterobacter aerogenes. These oils have antibacterial properties that vary according to their terpenoid content. Only the hybrid oil had a potent antioxidant effect, with an IC50 value of 4.21 ± 0.35 mg/mL for free radical (DPPH) scavenging. This oil's antioxidant effect may be a result of the phenolic terpenoids, thymol and carvacrol. As a result, these oils may be a novel source of antibacterial and antioxidant agents. Additionally, the antibacterial and antioxidant capabilities of the E. urophylla × E. camaldulensis hybrid essential oil are reported for the first time.

Synergistic Antimicrobial and Antioxidant Properties of Coccinia grandis (L.) Voigt, Clerodendrum inerme (L.) Gaertn. and Acanthus ebracteatus Vahl. Extracts and Their Potential as a Treatment for Xerosis Cutis.

BACKGROUND: A common health condition among older persons is xerosis cutis. Topical corticosteroid treatments are -associated with side effects. There is an unmet need for her-bal treatment alternatives. Coccinia grandis, Clerodendrum inerme and Acanthus ebracteatus are used to treat skin con-ditions in Thai traditional medicine. This study aimed to investigate their antimicrobial and antioxidant properties, synergistic properties as well as their cytotoxicity. METHODS: -Ethanolic herbal extracts were used to perform minimal -inhibitory (MIC) and minimal bactericidal concentration (MBC) assays on common skin pathogens. Synergistic anti-microbial activity was evaluated by a chequerboard assay. Antioxidant and synergistic properties were assessed by a 1,1-diphenyl-2-picrylhydrazyl assay. Cytotoxicity was tested on normal adult human primary epidermal keratinocytes. RESULTS: All extracts showed an inhibitory effect on growth of all microorganisms tested. MIC and MBC values ranged from 0.0625 to 32 mg/mL and from 0.0625 to >256 mg/mL, respectively. A. ebracteatus extract markedly demonstrated bactericidal activity against an methicillin-resistant Staphylococcus aureus strain. Additive antimicrobial activity was observed (fractional inhibitory concentration index values: 0.75-1). All extracts possessed antioxidant properties (IC50 values: 0.12-0.25 mg/L). However, antagonism was observed with paired extract combinations (combination index values: 1.025-1.455). The cell viability assay confirmed that herbal extracts were not cytotoxic. CONCLUSIONS: Our results provide early findings of pharmacological activities to support a novel choice of herbal combinations as potential local skin treatment options for xerosis cutis.

Antibacterial activity of cuminaldehyde on food-borne pathogens, the bioactive component of essential oil from Cuminum cyminum L. collected in Thailand.

Background Cuminum cyminum L., commonly known as cumin, has been traditionally used in Thai traditional medicine and traditional food flavoring. The present study investigated the chemical composition, antimicrobial activity against all tested major food-borne pathogenic bacteria, and bioactive components of essential oil extracted from C. cyminum L. collected in Thailand. Methods The main components of the essential oil were investigated by gas chromatography-mass spectrometry (GC-MS) technique. Antibacterial activities against Bacillus cereus, Staphylococcus aureus, Escherichia coli, and Salmonella Typhi were investigated by disk diffusion and microdilution method. The presence of the biologically active antibacterial components was also confirmed by the thin-layer chromatography (TLC)-bioautography. Results The main components of the essential oil investigated by GC-MS were cuminaldehyde (27.10%), beta-pinene (25.04%) and gamma-terpinene (15.68%). The essential oil exhibited antibacterial activity against B. cereus, S. aureus, E. coli and S. Typhi. The essential oil showed the strongest antimicrobial activity against B. cereus with a comparable inhibition zone to tetracycline. TLC confirmed the presence of biologically active antibacterial component in the essential oil against all tested food-borne bacteria. It is further demonstrated that cuminaldehyde was the most active compound in TLC-bioautography which inhibited all of tested bacteria. Conclusions Essential oil extracted from C. cyminum L. exhibited antibacterial activity against all tested major food-borne pathogenic bacteria. Cuminaldehyde is a major bioactive component. Our results suggest that the essential oil extracted from C. cyminum L. could be applied as an alternative natural preservative to control food-borne disease and have the potential for further development of new antibacterial agents.

Synthesis and activity of polyacetylene substituted 2-hydroxy acids, esters, and amides against microbes of clinical importance.

A series of novel polyacetylene substituted 2-hydroxy acids and derivatives were prepared and characterized. Alkylation of butane-2,3-diacetal (BDA) protected glycolic acid with iodoalkyl substituted polyacetylene compounds gave the corresponding diacetal protected polyacetylene substituted 2-hydroxy acids. Diacetal deprotection through acid mediated hydrolysis, transesterification or aminolysis afforded the 2-hydroxy-polyacetylenic acid, ester or amide derivatives. Twenty one of these novel compounds were tested against 10 microbes of clinical importance and several of them showed good antimicrobial activity, in particular against Pseudomonas aeruginosa.

Identification of Streptococcus uberis multilocus sequence types highly associated with mastitis.

Multilocus sequence typing analysis of Streptococcus uberis has identified a cluster of isolates associated with clinical and subclinical mastitis and a cluster associated with cows with low somatic cell counts in their milk. Specific groups of genotypes (global clonal complex [GCC] sequence type 5s [ST5s] and GCC ST143s) were highly associated (P = 0.006) with clinical and subclinical mastitis and may represent a lineage of virulent isolates, whereas isolates belonging to GCC ST86 were associated with low-cell-count cows. This study has, for the first time, demonstrated the occurrence of identical sequence types (ST60 and ST184) between different continents (Australasia and Europe) and different countries (Australia and New Zealand). The standardized index of association and the empirical estimation of the rate of recombination showed substantial recombination within the S. uberis population in Australia, consistent with previous multilocus sequence type analyses.