Aims: Many plants and their derivatives are widely used in food manufacturing because of their biological activities. They play a significant role as food additives to control microbial growth and the occurrence of oxidation reactions. Syzygium malaccense L. is a well-known plant with biological activities such as antimicrobial and antioxidant activities. Thus, the aims of this study were to evaluate the toxicity of the ethanolic leaves extract of S. malaccense and to study its antibacterial mode of action. Methodology and results: The toxicity assessment of S. malaccense leaves extract was determined using the brine-shrimp larvae model. The action mechanisms against bacterial membrane were determined by studying the intracellular material leakage by means of nucleic acid (DNA and RNA) release, crystal violet dye uptake and cellular protein leakage. The present findings proved the extract's safety as indicated by a high dose of 7.402 mg/mL for lethal concentration (LC50) against brine-shrimp larvae. On the other hand, the ethanolic extract caused a severe membrane permeability towards all the tested bacteria as indicated by the increased intracellular material leakage in a concentration-dependent manner. Conclusion, significance and impact of study The current study provides valuable information regarding the safety and antibacterial action mechanism of S. malaccense ethanolic leaves extract, thus paving the way for its utilization as a natural preservative in a wide range of food products.
Syzygium--toxicity ; Anti-Bacterial Agents

Introduction: There are numerous studies on the therapeutic properties of Artocarpus heterophyllus. However, studies on the aqueous extraction of A. heterophyllus leaves are limited. This present study was conducted to optimize the extraction conditions of A. heterophyllus leaves to yield the highest phenolic, flavonoids and antioxidant contents. Methods: Response surface methodology (RSM) was employed to obtain a higher phenolic extraction parameter(s) of A. heterophyllus leaves using Central Composite Design (CCD). The antioxidant activity was then determined via ABTS (2,29-azinobis (3 ethylbenzothiazoline-6-sulfonic acid)) and DPPH (2,2-Diphenyl-1-picrylhydrazyl) assay and analysis of the individual phenolics was performed by high performance liquid chromatography (HPLC). Results: The optimum extraction conditions with higher phenolics content and antioxidant activity was achieved at 81°C, 100 min and 40 mL/g sample with a good desirability value of 0.87. Under these optimized parameters, total phenolics and flavonoids were 174.48 ± 4.05 mg GAE/g sample and 21.44 ± 0.05 mg RE/g sample, respectively. Meanwhile, antioxidant activity via ABTS and DPPH assays were 90.88% ± 0.09 and 87.22% ± 0.62, respectively. Finally, under optimal extraction conditions revealed 4 compounds identified as chlorogenic acid, quercetin, rutin and kaempferol. Conclusion: The optimisation are promising to improve phenolic yield and antioxidant activity in A. heterophyllus leaves. It also proved that A. heterophyllus leaves can be used as an alternative natural antioxidant especially in medicinal applications since all identified compound possess significant biological activities for human health.