Hibiscus sabdariffa comprises calyx which is rich in flavonoids and numerous phytochemical compounds. Nevertheless, the extraction parameters can influence the recoveries of these bioactive compounds. It is then important to investigate the contributing effects of the process parameters and optimized their conditions to achieve higher recovery yield. Hence, this study was carried out to examine the contributing effects of microwave-assisted extraction (MAE) process factors (irradiation time, ethanol concentration, solvent/sample ratio, temperature, and microwave power) on the yield of total flavonoid (TF) contents from H. sabdariffa calyces using one-variable-at-a-time.The significant MAE process parameters were further optimized using Box Behnken design. At the MAE optimal conditions, the extract was analyzed to identify the flavonoid compounds using liquid chromatography-mass spectrometry quadrupole time of flight. An optimum TF content of 94.32 mg QE/g extract from H. sabdariffa calyces was obtained at the following MAE conditions: Irradiation time of 4 min; ethanol concentration of 52% vol/vol; microwave power of 450 W and solvent/sample ratio 15:1 ml/g. Moreover, 95 flavonoid compounds were tentatively identified in the extract at optimized MAE conditions. Thus, these flavonoids can be further isolated in future studies to unveil embedded potentials of H. sabdariffa calyx extract. Practical applicationThe procedure described the microwave-assisted extraction (MAE) which can serve as a guideline for extracting flavonoids from Hibiscus sabdariffa calyx. Moreover, the liquid chromatography-mass spectrometry quadrupole time of flight analysis provided the developed conditions for identifying flavonoids from the calyces. The results obtained suggested the exact MAE conditions to achieve an optimum yield of flavonoids from H. sabdariffa calyces. Most importantly, the tentatively identified flavonoids can further be isolated and purified in future studies to unveil the embedded biological potentials.

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Vernonia cinerea is one of the medicinal plants with several potentials for treating different ailments. In the present study, Microwave-assisted extraction (MAE) was employed in extracting phenolics compounds from this plant. However, different factors that affect this extraction method in the recovery of phenolics compounds abound, these factors need to be screened to determine actual contributing factor in order to minimize cost. Irradiation time (1-5 min), ethanol concentration (20-60% v/v), microwave power (40-80 W), extraction temperature (40-80 oC), and feed/solvent (1:10 - 1:18 g/mL) have been screened using two-factorial design for the recoveries of phenolic compounds from V. cinerea leaves. The results obtained in this study indicated that only microwave power, ethanol concentration, irradiation time and feed/solvent contributed to recoveries of total phenolic content (TPC) and total flavonoid content (TFC) from V. cinerea leaves. Thus, these factors at these ranges can be further optimized to obtain optimal yields of phenolic compounds from V. cinerea leaves.

Aloe vera is a perennial ethno-medicinal potential plant with a xerophytic characteristic, but not a cactus. It has a famous history owing to its phytopharmaceutical properties and this had made it useful in the pharmaceutical, cosmetic and food industries. Studies had shown the positive effects of its extract against bacteria, organisms. The phytochemical properties of A. vera have fungi, virus and parasitic been exploited for various economic and commercial purposes. This review contributes literature on the bioactive potential composition, processing and the pharmaceutical potential uses, an adverse side-effect that might spring up in case of over dosage and important safety precautions are summarized. More scientific innovations and developments in the aspect of analytical chemistry are on the way to provide more acceptable, purified chemical characterization of A. vera using sophisticated laboratory equipment and machines.

Nowadays, free radical chemistry is a field that has gained the wider attention of researchers. Our body generates free radicals’ reactive nitrogen and oxygen species through subjection to several pathological states, endogenous systems, and physicochemical conditions. For the physiological state to occur, it is compulsory to propel a balance between antioxidants and free radicals. Oxidative stress will set in when free radicals can no longer be regulated in the body system. Moreover, free radicals negatively affect DNA, protein, and lipids and cause many diseases in the human body. Thus, natural-sourced antioxidants can be used to manage this oxidative stress. Currently, it has been revealed that some synthetic antioxidants, including butylated hydroxyanisole and butylated hydroxytoluene, are hazardous to human health. Therefore, many efforts have been made in search of natural, non-toxic, and effective compounds that possess anti-oxidative properties. Hence, this review comprehensively presents the roles of plant-based antioxidants in resolving the challenging issues associated with free radical diseases in human beings. It further reviews the characteristics and occurrences of free radicals in the human body, the formation and mechanism of free radicals, some of the physiological impacts of free radicals on human health, sources of free radicals, and plant-sourced antioxidants as a frontier in managing free radicals.