Yau Yan Lim

Critical analysis of current methods for assessing the in vitro antioxidant and antibacterial activity of plant extracts

Natural product research is an active branch of science, driven by the increased value placed on individual health and well-being. Many naturally-occurring phytochemicals in plants, fruits and vegetables have been reported to exhibit antioxidant and antibacterial activity; often touted as being beneficial for human health. In vitro screening is a common practice in many research laboratories as a means of rapidly assessing these properties. However, the methods used by many are not necessarily optimal; a result of poor standardization, redundant assays and/or outdated methodology. This review primarily aims to give a better understanding in the selection of in vitro assays, with emphasis placed on some common assays such as the total phenolic content assay, free radical scavenging activity, disc-diffusion and broth microdilution. This includes a discussion on the reasons for choosing a particular assay, its strengths and weaknesses, ways to improve the accuracy of results and alternative assays.

Antioxidant Content, Antioxidant Activity, and Antibacterial Activity of Five Plants from the Commelinaceae Family

Commelinaceae is a family of herbaceous flowering plants with many species used in ethnobotany, particularly in South America. However, thus far reports of their bioactivity are few and far between. The primary aim of this study was to quantify the antioxidant and antibacterial activity of five Commelinaceae methanolic leaf extracts. The antioxidant content was evaluated by the total phenolic content (TPC), total tannin content (TTC), and total flavonoid content (TFC) assays. The antioxidant activities measured were DPPH free radical scavenging (FRS), ferric reducing power (FRP), and ferrous ion chelating (FIC); of the five plants, the methanolic leaf extract of Tradescantia zebrina showed the highest antioxidant content and activity, and exhibited antibacterial activity against six species of Gram-positive and two species of Gram-negative bacteria in a range of 5–10 mg/mL based on the broth microdilution method.

Investigation on the antimicrobial activities of gingers ( Etlingera coccinea (Blume) S.Sakai & Nagam and Etlingera sessilanthera R.M.Sm.) endemic to Borneo

To investigate the antimicrobial properties of Etlingera coccinea and Etlingera sessilanthera and to isolate and identify the antimicrobial compounds.

Identification of α‐tocopherol as a bioactive component of Dicranopteris linearis with disrupting property against pre‐formed biofilm of Staphylococcus aureus

The potential of Dicranopteris linearis leaves’ extract and its bioactive components were investigated for the first time for its disrupting ability against Staphylococcus aureus biofilms.

Comparison of physicochemical properties and aqueous solubility of xanthone prepared via oil-in-water emulsion and complex coacervation techniques

ABSTRACT The aim of this study was to enhance aqueous solubility of xanthone with natural polymers using oil-in-water emulsion and complex coacervation as the microencapsulation techniques. There was no interaction between xanthone and the wall material; and xanthone crystallinity was decreased as observed via fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and x-ray powder diffraction (XRD) after microencapsulation. Oil-in-water emulsion and coacervation increased xanthone solubility by 37-fold and 1.6-fold, respectively. However, O/W emulsion method required a high ratio of oil to xanthone. The solubilizing effect of oil and wall material, particle size reduction, and decreased crystallinity were responsible for enhancing the aqueous solubility of xanthone.

Current anti-biofilm strategies and potential of antioxidants in biofilm control

ABSTRACT Introduction: Biofilm formation is a strategy for microorganisms to adapt and survive in hostile environments. Microorganisms that are able to produce biofilms are currently recognized as a threat to human health. Areas covered: Many strategies have been employed to eradicate biofilms, but several drawbacks from these methods had subsequently raised concerns on the need for alternative approaches to effectively prevent biofilm formation. One of the main mechanisms that drives a microorganism to transit from a planktonic to a biofilm-sessile state, is oxidative stress. Chemical agents that could target oxidative stress regulators, for instance antioxidants, could therefore be used to treat biofilm-associated infections. Expert commentary: The focus of this review is to summarize the function and limitation of the current anti-biofilm strategies and will propose the use of antioxidants as an alternative method to treat, prevent and eradicate biofilms. Studies have shown that water-soluble and lipid-soluble antioxidants can reduce and prevent biofilm formation, by influencing the expression of genes associated with oxidative stress. Further in vivo work should be conducted to ensure the efficacy of these antioxidants in a biological environment. Nevertheless, antioxidants are promising anti-biofilm agents, and thus is a potential solution for biofilm-associated infections in the future.