Basil plant is a common source for linalool and estragole. However, it has been showed that the chemical composition of basil varies considerably depending on many factors including method of extraction, cultivar of the plant or geographical location. In this study, we attempted to extract essential oil from Vietnamese basil and analyze the chemical composition of the obtained oil using gas chromatography–mass spectrometry (GC-MS). The extraction method of choice was microwave-assisted hydro-distillation (MAHD) and the process was optimized with Response Surface Methodology (RSM) with regard to four experimental parameters including raw material size, raw material to water ratio, extraction time and microwave power. The results showed that ground basil leaves, when extracted with optimal conditions of water-to-material ratio of 3.2:1, extraction time of 97 (min) and microwave power of 430 (W), gave the actual essential oil yield of 0.6%. Regarding ANOVA results of the quadratic model, high determination coefficient (R2 = 0.9077), significant F-value of 10.92 and the p-value of less than 0.05 indicate that this model is significant between experimental and predicted variables, and should be fixed. In addition, GC-MS analysis revealed that major components of Vietnamese Basil were Estragole (87.869%), α-Bergamotene (2.922%), τ-Cadinol (2.770%), and Linalool (1.347%).

Black pepper (Piper nigrum L.) is a tropical crop with extensive medicinal potential in ethnomedicine and nutraceutical applications. The essential oil of black pepper finds wide applications in inhabitation of respiratory infections and soothing of muscular pains due to its warming and energizing property. The pungent bioactive piperine is responsible for this function, and therefore, efficient technology is required for an optimal extraction process of this compound. In the present article, we have developed a procedure for extracting black pepper essential oil from Vietnam, optimizing conditions that affect the extraction process. The effect of process parameters, namely material size, preservation method, the concentration of sodium chloride, the concentration of soak time, the ratio of material to water, temperature extraction, time extraction on the extraction yield, and relative efficiency were investigated. Results demonstrated that 20 g of black pepper milled with a mesh size of 160 obtained 0.48 g of essential oil (2.4%) at a raw material to water ratio of 1/21 (g/mL) at 150 °C in a time of 5.2 h. GC-MS (Gas chromatography–mass spectrometry) spectra showed that 3-carene (29.21%), D-limonene (20.94%), caryophyllene (15.05%), and β-pinene (9.77%) were present as major components. These results suggested that the essential oil extracted from Vietnamese black pepper is applicable in the manufacturing processes of insecticides and air deodorizers.

Microwave-assisted hydro-distillation (MAHD) is preferred to traditional extraction methods due to shorter extraction time, the inability of volatile components to be damaged or decomposed which in turn improve the efficiency and quality of essential oils. In this research, we investigated the parameters that affect the extraction of lemongrass oil process by MAHD method and compare with those of hydro-distillation (HD) method. Four parameters were identified which are: raw material size, raw material to water ratio, extraction time and microwave power. The results show that the optimum condition for determining the lemongrass essential oil content is 20 mm in the 90 min extraction time with a microwave power of 450 W at raw material to water ratio of 1:3 (g/mL). When compared to the HD method, we found that the yield lemongrass oil of MAHD method is 0.35% on 90 min and the yield of HD method is 0.2% on 360 min. The quality of oil samples at different extraction method was evaluated by determining their chemical constituents through GC-MS. The highest identified component is Citral with 93.28% for MAHD, while the HD was 83.85%. Therefore, MAHD method is highly efficient and shorten the time needed for the extraction of essential oils.

In the present study, the optimized solvent extraction conditions with regards to the total polyphenol content (TPC) and antioxidant capacity of rosemary leaf extract (RLE) were determined. The one-factor-at-a-time method was used to independently investigate the effect of several extraction parameters, including ethanol concentration (0–100% v/v), extraction temperature (50–80°C), extraction period (15–60 min), material–solvent ratio (1:5–1:10 g/mL), and extraction cycles (1, 2, and 3 times) on polyphenol content. Response surface methodology (RSM), in combination with a central composite design, was used to perform optimization. The following optimal conditions that gave maximal TPC were determined and experimentally verified: ethanol concentration of 65% (v/v), extraction temperature of 65°C, material–solvent ratio of 1:7.5 g/mL, extraction time of 15 min, and 2 cycles of extraction. These parameters corresponded with the TPC yield of 87.42 ± 0.25 mg gallic acid equivalent/g dried feed material (mg GAE/g DW). The optimal conditions gave a high extraction yield (337 ± 6 mg dried extract/g dried feed material) with 197.28 ± 3.11 mg GAE/g dried extract. The estimated models were strongly significant (p < 0.05) for TPC values with significant regression coefficients (R 2) of 0.9979. The obtained RLE was supposed to be the top grade of natural antioxidant with the IC50 (DPPH assays) value of 9.4 ± 0.1 μg/mL, which is higher than that of the vitamin C by just three times (IC50 = 3.2 ± 0.1 μg/mL). Current results justify RLE as a potential agent in food preservation applications.

In this research, the hydrodistillation extraction method has been adopted to extract the essential oil from Vietnamese Mandarin (Citrus reticulata Blanco) peel purchased from Thu Duc, Vietnam. Various extraction conditions influencing the oil yield were investigated. The obtained essential oil was evaluated for physicochemical characteristics. GC–MS studied the chemical composition of the oil. The results showed that with the ground Mandarin peel, the ratio of peel to solvent ratio 1:4 (g/mL), extraction time of 150 minutes at a temperature of 110-120°C, the highest essential oil yield was attained at 5%. Bioactive components found at high content included limonene (97.655%), were followed by β-Myrcene (1.395%), 1R-α-Pinene (0.561%), L-β-pinene (0.264%), Sabinene (0.126%).