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The present study has focused on the extraction and utilization of antioxidant compounds from the agricultural produce Zingiber officinale for its sustainable use in terms of stabilizing food from oxidation. Two extraction methods, traditional soxhlet and green supercritical CO2 (SC-CO2), were used to compare yields of antioxidant (6-gingerol) rich extracts. For the SC-CO2 method, operating parameters including pressure (10000-20000 kPa), temperature (30- 40°C) and CO2 flow rate (5-20 g/min.) were optimized to get maximum recovery of [6]-gingerol rich extracts. The results of the extraction study revealed that ginger extract collected after soxhlet extraction (GE1) gives more yield (3.85%) than the extract (2.41%) collected after SC-CO2 extraction (GE2) at an optimum condition of 20000 kPa pressure, 40°C temperature and 20 g/min. flow rate. Contrarily, the yield of [6]-gingerol was found to be greater in GE2 (389 mg/g) than GE1. Total phenol (TPC) and flavonoid (TFC) content of GE1 and GE2 were measured against equivalent concentrations of gallic acid and quercetin. TPC and TFC of GE1 show slightly higher values (38.50 mg GAE/g, 5.62 mg QE/g) than GE2. At the concentration of 3000 μg/mL, DPPH percent inhibition activity of GE1 was again higher (up to 94%) than GE2 (up to 82%). Stability study result of both GE1 and GE2 revealed on the basis of antioxidant indices, showed desirable antioxidant index by stabilizing all three experimented oils and also found to be comparable with synthetic antioxidants (BHA, BHT). Therefore, it could be concluded that [6]-gingerol rich extracts from the SC-CO2 method have comparable phenol flavonoid, antioxidant and stability potential as those found in ginger extracts from the traditional soxhlet method.

Four leafy vegetable species, spinach (Spinacia oleracea), amaranthus (Amaranthus viridis), fenu-greek (Trigonella foenum-graecum) and bathua (Chenopodium album), were extracted with three different solvents (80% ethanol, 80% acetone and water) for maximum recovery of phenol and antioxidant compounds in the extract. The results of extraction were compared with extraction from moringa (Moringa oleifera) leaves that is known as a very rich source of antioxidants. The study showed that, it is very difficult to justify a single solvent for extraction of antioxidant compounds from different plants. Results from different solvents used for extracting the bioactive compounds mostly depend on the type of compound extracted (polar/medium polar/non-polar) present in leafy matrices. Here, 80% acetone extract showed highest total phenol content in moringa leaves but the overall antioxidant activity in the leaves of four vegetables was observed to be better after extraction with 80% ethanol. Nevertheless, in most assays, independent of solvent used for extraction, the moringa leaves were the richest source of polyphenols and antioxidants.

Biodiesel, fatty acid methyl ester produced by the transesterification of vegetable oil with methanol, is a promising alternative to petroleum-based diesel fuel. In the present study, the methanolysis of high free fatty acid (FFA) Jatropha curcas oil in a transesterification reaction using K2CO3 /CaO solid base catalyst was studied. The various reaction parameters in the transesterification reaction were also discussed. The catalyst was characterized by means of Fourier transform infrared, X-ray diffraction, temperature programmed desorption of CO2 , scanning electron microscopy, particle size analyzer, true density, and surface area analyzer. The optimum conversion of jatropha oil was 92% when the transesterification reaction was carried out at 70 °C with 10:1 molar ratio of methanol to oil at reaction time of 3 h and catalyst amount of 6 wt%. The efficiency of catalysts in the methanolysis of jatropha oil was also investigated. [ABSTRACT FROM AUTHOR]