Extraction, optimisation and characterisation of phenolics from Thymus vulgaris L.: phenolic content and profiles in relation to antioxidant, antidiabetic and antihypertensive properties

Abstract

The objectives of this study were to examine varying extraction conditions of Thymus vulgaris L. as related to phenolic content and profiles of the extracts and their antioxidant, antihypertensive and antidiabetic properties. Phenolics were extracted under various conditions pertaining to free and bound phenolics, solvent type and combination of extraction time and temperature, and these extracts were evaluated in terms of their antioxidant activities and inhibitory activities of angiotensin-converting enzyme (ACE), a-glucosidase and a-amylase. The acetone-water solvent mixture (1:1; v/v) produced the extract with the greatest phenolic content, antioxidant activity and inhibitory activities of ACE and a-glucosidase. The optimal extraction temperature for maximum phenolic content and antioxidant activity associated with methanol extraction was 60°C, whereas a lower temperature at 40°C was required to maximise inhibitory activities for ACE, a-glucosidase and a-amylase. An inverse relationship was seen between antioxidant and glucosidase inhibitory activities vs. the ACE and a-amylase inhibitory activities, which suggests the need for extractions to be directed to specific bioactivities of thyme extracts. Generally, the results indicate major differences in phenolic profiles among the tested extraction conditions with thymol as the predominant phenolic seen in most extractions, while gallic acid, rosmarinic acid or diosmin also predominated in other extracts. Extracts with the same predominant phenolic compound and similar phenolic content showed major disparities in their ACE, glucosidase and a-amylase inhibitory activities, indicating that the major phenolic profiles of thyme extracts may not be necessarily related to the degree of inhibition of ACE, glucosidase and a-amylase enzymes. Biological properties of extracted phenolics from thyme M. H. Alu'datt et al. 721 Biological properties of extracted phenolics from thyme M. H. Alu'datt et al. ND, Not detected; *percentage of total phenolic content based on peak areas. The values are means for two replicates AESD (standard deviation); SE, standard error. Values with different letters in the same column are significantly different at P ≤ 0.05. Biological properties of extracted phenolics from thyme M. H. Alu'datt et al.

Phytochemical Composition and Antioxidant, Anti-Acetylcholinesterase, and Anti-α-Glucosidase Activity of Thymus carnosus Extracts: A Three-Year Study on the Impact of Annual Variation and Geographic Location

“…At 1 mg/mL, T. carnosus extracts presented an α-glucosidase inhibition ~2.16 times and 2.71 times higher than T. fragrantissimus [ 30 ] and T. pulegioides [ 24 ] extracts at 0.5 mg/mL (the only concentration tested). Aqueous extracts of T. vulgaris (concentration not mentioned) were reported to inhibit 4% and 20% of α-amylase and α-glucosidase, respectively [ 50 ], which are also in-line with the results were reported. Therefore, T. carnosus extracts present a moderate potential for the reduction of post-prandial blood sugar uptake by inhibiting α-glucosidase.…”

The Effect of Open Field and Foil Tunnel on Yield and Quality of the Common Thyme (Thymus vulgaris L.), in Organic Farming

“…These results, indicating the increase of flavonoids in herb with successive cuts, correspond with those obtained in the previous experiment, conducted on the sweet basil [24]. According to literature data, the content of phenolics in common thyme herb depends on various factors, i.e., the origin of plants and/or methods of extraction and purification [13,14,54,55].…”

“…Phenolic acids are represented mainly by rosmarinic and caffeic acid [11][12][13][14]. Triterpenes (derivatives of ursolic and oleanolic acids) have also been identified in the herb of thyme [4].…”

Bioactive Peptides

“…Since foods may contain several other non-protein bioactive compounds, it is advisable to separate such compounds from the food proteins to avoid interference. For instance, phenolic compounds are known for their antioxidant [ 25 ], antihypertensive, antidiabetic [ 26 ] and antimicrobial [ 27 ] abilities and hence, when present in hydrolysates, can interfere with the biological activities being assayed. Phenolic compounds could be separated from food proteins using methods such as ethanol extraction [ 24 ], supercritical carbon dioxide [ 28 ] pressurized water extraction [ 29 ], ultrasound-assisted extraction [ 30 ] and acetone extraction [ 31 ] prior to enzymatic hydrolysis.…”