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shaken for about 10 min and optical density of the purple precipitates was measured at 560

nm in a microplate reader (Tecan Spark, Tecan). Viability of the cells was expressed in
percent (%) of control as below.

CV (%) = OD of treated cells/ OD of control cells × 100
Dose-response curves were plotted and the concentrations of the plant extracts that caused

50% of inhibition of cell viability (IC50) were determined by using GraphPad Prism 8
software.

RESULTS AND DISCUSSION

Phytochemical determination of S. acmella illustrated the presence of abundant
phenolics and flavonoids primarily in the leaves and flowers of the plant. The highest

phenolic (434.39±6.34 mgGAE/g) and flavonoid (238.70±13.14 mgQE/g) contents were

observed in the leaves of the plant (Fig. 2). Phenolic and flavonoid compounds are important
classes of secondary metabolites that play vital roles in many biological functions of plants

and animals such as antimicrobial, antioxidant, anti-inflammatory, antidiabetic, anticancer etc
[19]. Most of these compounds have unique nature of donating electrons because of hydroxyl

groups attached to the aromatic ring that help in scavenging harmful free radicals such as
͞
•
superoxide radical (O2 ), hydroxyl radical (HO ), hydrogen peroxide (H2O2) etc [20].
Excessive accumulation of these free radicals may be harmful as it could affect systemic

biology thereby damaging DNA, RNA, proteins and lipids in the body [21]. Consumption of
fruits and vegetables enriched with natural phenolic and flavonoid compounds helps in the

prevention and treatment of several oxidative stress induced toxicities and diseases such as
cardiovascular diseases, atherosclerosis and neurodegenerative diseases like Parkinson's

disease, Alzheimer's disease, multiple sclerosis etc [22]. Here, antioxidant assays illustrated
•
•+
high ABTS and DPPH scavenging properties of methanol extracts of leaf, flower and stem

of S. acmella. Free radical scavenging activities of the plant extracts were increased with an
increase in their respective concentrations (Fig. 3). The IC50 values of the leaf, flower and
stem extracts of S. acmella for scavenging ABTS •+ were 11.92, 13.18 and 20.85 µg/ml

respectively. Similarly, the leaf, flower and stem extracts of the plant showed comprehensive
•
scavenging of DPPH with IC50 values of 14.79, 16.64 and 29.64 µg/ml respectively. Here the
lowest IC50 values of the leaf extracts correspond to the highest antioxidant potential.

However the free radical scavenging effects of the plant extracts were comparatively lower
than ascorbic acid (100 mM).

Comprehensive analysis of metabolites present in different parts of S. acmella using
GC-MS revealed a fingerprint of several bioactive compounds having antioxidant, anti-

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