Comparative Study of Photoprotective and Antioxidant Potential of Manjistha (Rubia Cordifolia) and Agastache (Agastache Rugosa) Extracts

Gnanamuthu, Trishcia (2026) Comparative Study of Photoprotective and Antioxidant Potential of Manjistha (Rubia Cordifolia) and Agastache (Agastache Rugosa) Extracts. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Natural plant extracts are rich sources of bioactive compounds with potential applications in skincare and photoprotection. This study aimed to evaluate the antioxidant activity and photostability of Manjistha (Rubia cordifolia) and Agastache extracts. Phytochemical screening revealed the presence of flavonoids, tannins, terpenoids, phenols, and saponins, while alkaloids (Mayer’s and Wagner’s tests) were absent. Antioxidant activity was assessed using DPPH, FRAP, and ABTS assays at concentrations of 20, 50, 100, and 200 μg/mL. Manjistha extract exhibited increasing % scavenging in DPPH assay with concentration, reaching a mean of 68.47% at 100 μg/mL (IC₅₀ = 58.5 μg/mL), while Agastache reached 62.91% at the same concentration (IC₅₀ = 58.7 μg/mL). FRAP results indicated higher Trolox equivalent antioxidant capacity for Manjistha compared to Agastache at all tested concentrations. ABTS assay confirmed a dose-dependent increase in radical scavenging, with both extracts showing maximum scavenging at 200 μg/mL. Photostability tests under UV light (310 nm) and in dark conditions showed minor fluctuations in UV-Vis absorbance over 120 minutes, indicating relative stability of the extracts. Corresponding DPPH scavenging after UV exposure remained consistent with initial values, suggesting retention of antioxidant activity. Overall, the results demonstrate that both Manjistha and Agastache extracts possess antioxidant properties and maintain stability under short-term UV exposure, highlighting their potential for future studies in photoprotective applications.