Variations in Total Phenolic, Total Flavonoid Contents, and Free Radicals’ Scavenging Potential of Onion Varieties Planted under Diverse Environmental Conditions

Abstract

Genetic diversity and Agro-climatic conditions contribute significantly to the agronomic and morphological features of the food plant species, and their nutraceutical potential. The present study was intended to evaluate the impact of growing conditions on total phenolic and total flavonoid contents, and in vitro antioxidant potential in the bulbs and leaves of onion varieties planted under diverse environmental conditions. Standard analytical methods were used to quantify total phenolic content (TPC), total flavonoid content (TFC), and free radicals’ scavenging/antioxidant capacity. The impact of climatic and soil conditions was assessed using statistical tools. In general, onion varieties cultivated at three different locations viz. Kalar Kahar, Lahore and Swabi exhibited significant variations in TPC and TFC, and antioxidant activities. The bulbs and leaves of Mustang (V1) variety planted at Lahore and Swabi had significantly (p < 0.05), high levels of TPC (659.5 ± 6.59, and 631.1 ± 8.58 mg GAE/100 g, respectively). However, leaves of Red Orb (V2) and bulbs of Mustang (V1), and Golden Orb (V6), harvested from Kalar Kahar depicted the highest concentration of TFC (432.5 ± 10.3, 303.0 ± 6.67, and 303.0 ± 2.52 mg QE/100 g DW, respectively). Likewise, bulbs of V1 planted at Kalar Kahar, Lahore and Swabi exhibited maximum inhibition of DPPH, ABTS, and H2O2 radicals (79.01 ± 1.49, 65.38 ± 0.99, and 59.76 ± 0.90%, respectively). Golden Orb (V6) harvested from Lahore had the highest scavenging of OH radical (67.40 ± 0.09%). Likewise, bulbs of V1 variety planted at KalarKahar and Swabi had significant capacity to scavenge ferric ions (415.1 ± 10.6 mg GAE/100 g DW), and molybdate ions (213.7 ± 0.00 mg AAE/100 g DW). Conversely, leaves of Amazon (V8), planted at Lahore and Swabi depicted significant levels of DPPH, ABTS, H2O2 radical scavenging (90.69 ± 0.26, 63.55 ± 1.06, 51.86 ± 0.43%, respectively), and reduction of ferric ions (184.2 ± 6.75 mg GAE/100 g DW). V6 leaves harvested from Lahore and that of Super Sarhad (V3) from Swabi showed the highest inhibition of OH radical (61.21 ± 0.79%), and molybdate ions (623.6 ± 0.12 mg AAE/100 g DW), respectively. Pearson correlation and principal component analysis revealed strong relationships of climatic conditions, soil properties and elevation with TPC, TFC and free radicals’ scavenging potential in the bulbs and leaves of onion varieties. The variations in the total phenolic and flavonoid contents, and antioxidant potential of different varieties, and their associations with climatic and soil factors revealed the complexity of the growing conditions and genetic makeup that imposed significant impacts on the synthesis of secondary metabolites and nutraceutical potential of food and medicinal plant species.

Synergistic effect of Trikatuk, a traditional Thai formulation, on antioxidant and alpha-glucosidase inhibitory activities

“…The Pearson's correlation coefficients also revealed that TPC and TFC were significantly correlated with the ABTS and DPPH radical scavenging capacities. Similar to our results, many studies have consistently reported a correlation between antioxidant activity estimated by ABTS and DPPH assays and the TPC and TFC values [ 23 , 26 , 28 , 29 ]. This suggests that ZO, with the highest TPC and TFC values, could be the main contributor to the antioxidant function of Trikatuk.…”

“…The antioxidant capacity was evaluated by the ABTS and DPPH assays which are simple, rapid, inexpensive, acceptable, and widely used [ 21 , 26 ]. DPPH is the free radical most commonly used in antioxidant screening assays where the capacity of each extract could be classified as very strong (IC 50 < 50 μg/mL), strong (IC 50 50–100 μg/mL), moderate (IC 50 101–150 μg/mL), and weak (IC 50 > 150 μg/mL) [ 27 ].…”

Impression of foliar-applied folic acid on coriander (Coriandrum sativum L.) to regulate aerial growth, biochemical activity, and essential oil profiling under drought stress

“…With relevance to the abovementioned facts, the results of the present study demonstrated the increased production of bioactive compounds like TPC and TFC under MS75 and SS50 due to water deficit conditions. These are the secondary metabolites that assist the plant to maintain the osmotic balance and thus cope with water stress scenarios (Mashkor and Muhson, 2014;Bibi et al, 2022;Rahimi et al, 2022). Hence, the foliar supplementation of FA presented non-significant results of TPC and TFC at all levels of irrigation regimes (Figure 10).…”

Identification of potential anti‐Alzheimer agents from Pistacia atlantica Desf. galls using UPLC fingerprinting, chemometrics, and molecular docking analyses

“…Studies have revealed that extracts prepared from the same plant species but collected at different times of the year and/or different locations can present significant differences in their chemical profiles, which in turn affects biological activity (Bibi et al, 2022;Reyes-Vaquero et al, 2021;Shi et al, 2022). The could be due to the presence of defensive compounds targeting these enzymes in insects (Ryan & Byrne, 1988).…”