Stress-Driven Changes in Ascorbic Acid Levels in Raphanus Sativus: A Comparative Study

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Abstract
Abiotic stresses such as extreme temperatures and salinity are known to significantly influence the nutritional quality of vegetables during cultivation and postharvest handling. However comparative study on how different abiotic stresses alter ascorbic acid stability in root vegetables like red radish is understudied. Thus, the present study was conducted to evaluate the effect of various abiotic stresses (heat, cold and salinity) on ascorbic acid (AA) levels and antioxidant activity in red radish (Raphanus sativus L.). DCPIP titration and DNPH UV-Vis spectrophotometric techniques were used to analyse the ascorbic acid content, and the DPPH radical scavenging assay was used to measure antioxidant capacity. The findings showed that as stress duration and intensity increased, the total AA content decreased significantly (p < 0.05). At high temperature (90 °C), heat treatment resulted in a progressive decrease from 27.7 mg/100g to 20.8 mg/100g. Under cold stress, AA content increased slightly initially and then dropped by 22% on day 8. A two-phase response to salt stress was seen mild salt concentration leading to a moderately increased AA content, while severe salt concentration caused a 55% reduction after 72 hours. With an IC₅₀ value of 8.27mg/mL, the antioxidant activity increased as extract concentration increased from 3.8% to 62.1% inhibition. According to these findings, red radish exhibits a short-term adaptive defence in mild stress situations but a significant decrease in AA in severe stress situations. These findings are consistent with previous reports in other related vegetables such as tomato, broccoli and spinach, where moderate abiotic stress increases antioxidant defences before degradation occurs. These results suggest the need for efficient postharvest management and stress-aware storage techniques to preserve the functional and health-promoting qualities of red radish.

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