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Background: Black- and white pepper extracts are natural products, which had been extensively used in food industries as a seasoning agent, and in herbal medicine for the treatment of many free radical-related diseases. Owing to the medicinal and nutritive benefits of this functional spice, the need then arises to find a way of extracting its fixed oil at optimum condition. Objectives: The aim of this study was to investigate the effect of extraction parameters on the extraction yield, antioxidant activities, microstructure, functional group characteristics, and elemental composition of fixed oils extracted from the two cultivars. Methods: Extraction of fixed oil was carried out using a heat reflux extraction technique. The dietary elemental composition was conducted using Energy Dispersive Spectroscopy (EDS). The effect of localized heating on the extracts was evaluated to determine the structural changes in the pepper sample using Brunauer-Emmett-Teller (BET) and Scanning Electron Microscopy (SEM). Results: The optimal fixed oil yields under the optimum condition were 10.38 mg/g for the black pepper and 15.27 for the white pepper. The antiradical powers (ARP) of 0.007985 and 0.009046 mL/µg were obtained for black- and white pepper fixed oil, respectively. This suggests that the fixed oil from white pepper exhibited higher antiradical characteristics than black pepper fixed oil. The results of BET-parameters revealed the percentage of deformations related to the black- and white pepper under the localized heating was 21.47% and 29.14%, respectively. Conclusions: The results revealed a greater deformation on the microstructure of white pepper than black pepper. Moreover, rich dietary elements present in the extracts succinctly unveiled the potential of fixed oil extracts in curative applications and preventive traditional medicine.

Vernonia amygdalina leaf has a significant importance in food and traditional medicine. It has been reported to possess various pharmacological effects. This study was carried out to investigate the influence of microwave-assisted extraction factors on the extraction from V. amygdalina leaves. The results highlighted that an increase in temperature deteriorated the yields of V. amygdalina leaf. Thus, shade-dried samples gave the highest yields at the irradiation times of 10 and 2 min, microwave power of 500 and 600 W, the temperature of 100 and 80°C, the feed-to-solvent ratio of 1:10, and ethanol concentration of 60% v/v using water and ethanol as the extracting solvents, respectively. Likewise, the antioxidant assay resulted in IC50 values of 260 ± 1.1 µg/mL DPPH and 149.78 ± 0.81 µg/mL ABTS for water and 204 ± 0.92 µg/mL DPPH and 31.17 ± 1.4 µg/mL ABTS for ethanol. Therefore, the synergistic mechanism of mass and heat transfer may be accounted for the accelerated extraction due to microwave energy.