Optimized extraction of polyphenols from leaves of Rosemary (Rosmarinus officinalis L.) grown in Lam Dong province, Vietnam, and evaluation of their antioxidant capacity

Abstract

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.

Salvia rosmarinus Spenn. (Lamiaceae) Hydroalcoholic Extract: Phytochemical Analysis, Antioxidant Activity and In Vitro Evaluation of Fatty Acid Accumulation

“…Since these authors used a conventional method of extraction, this difference may be ascribed to the environmental conditions, as the chemical composition of rosemary can be affected by soil properties [ 53 ], fertilizers [ 54 ], saltiness [ 55 ], humidity and temperature [ 56 ]. Furthermore, Balouiri et al, using a 22-h two-step maceration with hexane and methanol, were able to achieve an extraction yield of 15.8%, in line with our data, whereas, using an ultrasonic extraction, a yield of 8.7% was obtained [ 52 ].…”

“…Each gram of rosemary underwent extraction, corresponding to a total percentage yield of 13.1%. This percentage was in line with data reported by Lamponi et al, from another Italian rosemary collected in Tuscany [ 40 ], but our yield was different from the data published by Jacotet-Navarro et al or by Nguyen-Kim et al, which reported extraction yields of around 25% and 33%, respectively, with 75% EtOH for S. rosmarinus collected in Morocco [ 47 ] and in Vietnam, respectively [ 52 ]. Since these authors used a conventional method of extraction, this difference may be ascribed to the environmental conditions, as the chemical composition of rosemary can be affected by soil properties [ 53 ], fertilizers [ 54 ], saltiness [ 55 ], humidity and temperature [ 56 ].…”

Chemical Composition of Rosemary (Rosmarinus officinalis L.) Extract and Its Inhibitory Effects on SARS-CoV-2 Spike Protein–ACE2 Interaction and ACE2 Activity and Free Radical Scavenging Capacities

“…As a result, they found that the optimized conditions for their study were when the ethanol was 65% (v/v), the temperature was 65 °C, and the material-to-solvent ratio of 1:7.5. At this point, the TPC value was 87.42 mg GAE/g, which was higher compared to the results found in the current study or other previous studies …”

“…In another study, 60% acetone was used as a solvent for the rosemary extraction, and that extract had a TPC value of 68 mg GAE/g . Further, Nguyen et al investigated the optimized condition for the TPC value of rosemary extract . Their study controlled three factors, including ethanol concentration in a solvent, temperature, and the material-to-solvent ratio.…”

Sustainable Recovery of Phenolic Compounds from Distilled Rosemary By-Product Using Green Extraction Methods: Optimization, Comparison, and Antioxidant Activity

“…Although maceration is a conventional and widely used solid–liquid extraction technique for obtaining antioxidants from rosemary tissues [ 19 ] because of its simplicity, easiness to scale up, and low cost, it is characterized by prolonged extraction times, substantial amounts of solvents, many extraction steps, and higher energy consumption. Soxhlet extraction is widely used at the lab scale for recovering phenolic-rich extracts.…”