A Comparison of the Antioxidative and Anti-Diabetic Potential of Thermally Treated Garlic, Turmeric, and Ginger

Abstract

Spices have been used for centuries for food preservation, flavors, and medicinal properties. Research suggests that garlic, turmeric, and ginger contain potent antioxidants that may prevent and/or delay chronic diseases such as cancer, diabetes, and heart disease. Heat treatment of spices may potentially increase antioxidative activity by modifying the inherent chemical structure of potent antioxidative compounds within spices. The purpose of this study was to determine the impact of thermal treatment of garlic, ginger, and turmeric on total phenolic content (TPC), total flavonoid content (TFC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, ferric reducing antioxidant potential (FRAP), trolox activity (TEAC), lipase, a-amylase, and a-glucosidase inhibition. Conventional stovetop heating of selected spices was performed followed by methanolic and aqueous extractions (1-5 minutes; 70˚C-130˚C). Overall methanolic extracts had higher phytochemical, antioxidative, and anti-diabetic potential. However, aqueous garlic extracts exhibited higher phytochemical and antioxidative potential over methanolic garlic extracts. The highest TPC for aqueous garlic extracts was observed at 1 minute (14.11 mg GAE/g) while methanolic garlic extracts at 1 minute were significantly lower (1.72 mg GAE/g). Methanolic turmeric extracts had highest TPC at 5 minutes (28.55 mg GAE/g). Time and temperature influenced antioxidant activity in the spices. Turmeric and ginger (methanolic extracts) resulted in higher percent inhibition of DPPH radical with an increase in time (5 minute) turmeric (86.9%) and ginger (79.09%) at 7.9 mg/mL concentration. The results of this study revealed both solvent and time for thermal treatment of spices influenced antioxidative potential as determined using DPPH and FRAP assays. Therefore, the use of thermal application on spices presents promise in potentiating the antioxidant content and thereby their potential health promoting properties.

Comparative Study of Chemical Composition and Antioxidant Activity of Essential Oils and Crude Extracts of Four Characteristic Zingiberaceae Herbs

“…In the case of the ginger rhizome, the highest TPC value (9.63 ± 0.05 mg GA g −1 DW) was found in the methanolic extract, while water resulted in the lowest TPC content (6.42 ± 0.33 mg GA g −1 DW). Similar results were observed in the study by Hester et al [ 70 ].…”

Antioxidant, antibacterial and antiviral effect of the combination of ginger and garlic extracts

“…Methanolic extracts derived from ginger samples have demonstrated elevated phenolic content, whereas aqueous extracts obtained from garlic samples have exhibited heightened phenolic content. The occurrence of fat-soluble phenolic compounds, including hydroxybenzoic acid, within methanolic extracts of garlic could potentially contribute to the observed elevation in overall phenolic content [ 36 ]. Thus, total phenolic content serves as a screening parameter for antioxidant activity in plants [ 37 ].…”

“…Other studies have demonstrated heightened oxidation activities in ginger and garlic organic extracts [ 22 , 39 , 40 ]. The heightened presence of phenolic compounds in ginger potentially contributes to its superior antioxidant activity and capacity for scavenging free radicals when compared to garlic [ 36 ]. Furthermore, combination of both exhibited significant increase (85.44%; p < 0.005) in antioxidant activity even at lower concentrations (6 mg/ml) as given in Figure 1 .…”

Phenolic Bioactives From Plant-Based Foods for Glycemic Control

“…The improvement in human health protective antioxidant, anti-hyperglycemic, anti-hypertensive, and anti-microbial functional qualities in sprouts and beans following thermal processing might be due to oxidation and polymerization of phenolic bioactives and subsequent modification in their structure-function relationship. Previously, thermally treated (toasted in conventional stove-top) spices (ginger- Zingiber officinale , garlic- Allium sativum , and turmeric- Curcuma longa ) showed high phenolic linked antioxidant and enhanced α-glucosidase enzyme inhibitory activity ( 116 ). In another study, Hester et al ( 115 ) found induced antioxidant activity in Wistar male rat following feeding with thermally treated garlic, ginger, and turmeric.…”