Abstract
This study evaluated the efficacy of various organic solvents (80% acetone, 80% ethanol, 80% methanol) and distilled water for extracting antioxidant phenolic compounds from turmeric, curry leaf, torch ginger and lemon grass extracts. They were analyzed regarding the total phenol and flavonoid contents, antioxidant activity and concentration of some phenolic compounds. Antioxidant activity was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay and the ferric reducing antioxidant power (FRAP) assay. Quantification of phenolic compounds was carried out using high-performance liquid chromatography (HPLC). All the extracts possessed antioxidant activity, however, the different solvents showed different efficiencies in the extraction of phenolic compounds. Turmeric showed the highest DPPH values (67.83–13.78%) and FRAP (84.9–2.3 mg quercetin/g freeze-dried crude extract), followed by curry leaf, torch ginger and lemon grass. While 80% acetone was shown to be the most efficient solvent for the extraction of total phenolic compounds from turmeric, torch ginger and lemon grass (221.68, 98.10 and 28.19 mg GA/g freeze dried crude extract, respectively), for the recovery of phenolic compounds from curry leaf (92.23 mg GA/g freeze-dried crude extract), 80% ethanol was the most appropriate solvent. Results of HPLC revealed that the amount of phenolic compounds varied depending on the types of solvents used.
Highlights
In recent years, natural phytochemicals existing in herbs and spices have been widely used to cure, inhibit or reduce the risk of human diseases [1,2]
Acetone extract of turmeric exhibited the highest quantity of total phenol content (221.7 mg gallic acid equivalent (GAE)/g of freeze-dried crude extract (CE) while water extract of lemon grass demonstrated the lowest amount to total phenolic compounds (1.2 mg GAE/g CE)
The higher total phenolic content in 80% acetone solvent extraction of turmeric may be due to the fact that major phenolic compounds of turmeric are made of a long nonpolar chain of carbon–carbon covalent bonds with a phenolic group attached to the two ends [12]
Summary
Natural phytochemicals existing in herbs and spices have been widely used to cure, inhibit or reduce the risk of human diseases [1,2]. Phenolic compounds, including phenolic acids and flavonoids, are the major groups of natural components in plants which have received increasing interest over the last decades due to free radical scavenging properties. These bioactive compounds vary in type, number and position of functional groups, resulting in variations in chemical properties which can influence the solubility of these compounds in different solutions [4]. It is reported that the profile of phenolic compounds extracted from material is dependent on the polarity of the solvents used for extraction [5,6,7]. Selecting the best solvent is a key factor which impacts the quality and quantity of extracted phenolic compounds
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