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28 INNOSC Theranostics and Pharmacological Sciences, 2022, Vol. 5, No. 2 Madhavamurthy et al.
A B C

D E

Figure 2. The antibacterial activity of the maximum zone of inhibition showed in methanolic extracts
of Dendrobium jerdonianum. (A) Salmonella typhi, (B) Shigella flexneri, (C) Pseudomonas aeruginosa,
(D) Escherichia coli, and (E) Bacillus subtilis.
Notes: N: Negative control; S: Standard.

inhibited the growth of bacteria, a finding in line results revealed that the aqueous extract showed
with the report of Bhatnagar and Ghosal (2018), who excellent antioxidant activity, followed by the
demonstrated that methanolic extracts effectively methanol and chloroform extracts. The assay also
inhibit E. coli, S. aureus, and Acinetobacter sp. It revealed a dose-dependent with RSA. Furthermore,
was also noticed that the zone of bacterial inhibition Paudel et al. reported the antioxidant activity
was also increased with plant extracts in a dose- of D. moniliforme, wherein the ethanol extracts
dependent manner [35]. showed antioxidant properties of 94%, significantly
higher than acetone and chloroform extracts [37].
3.3. Antioxidant activity
3.4. Total phenolic content (TPC)
The antioxidant activity of each plant extract
was evaluated using the DPPH method. The The total phenolic content was measured and quantified
percentage of RSA was measured, and the results in terms of gallic acid equivalent. These plants are
are presented in Table 3. Among the tested often associated with polyphenolic substances and
plant extracts, aqueous extracts of P. pallida, are considered a good source of antioxidants. Orchid
D. jerdonianum, and B. Neilgherrensis exhibited plants, in particular, are well-known for their own
antioxidants properties of 91%, 81%, and 74%, medicinal properties (Moretti et al., 2013) [38]. The
respectively, with inhibitory concentrations (IC ) phenolic content was measured according to the
50
of 55.68, 43.72, and 54.84 μg/mL. The methanol Folin–Ciocâlteu method at 100 μg/mL, and the results
and chloroform extracts of D. barbatulum and are presented graphically in Figure 3. The assay
E. mysorensis showed significant RSA of 83% and revealed that all the extracts contained a considerable
85% at higher concentrations, with IC values of amount of polyphenols. The percentage of TPC
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44.02 and 36.49 μg/mL, respectively. The standard was determined by referencing the plotted standard
gallic acid showed 94% inhibition at 100 μg/mL gallic acid curve and applying a linear regression
(IC = 30.49 μg/mL), and it was dose-dependent. coefficient with an R² value of 0.9986 (FigureS2).
50
Similar results on medicinal orchids have been Among the tested plant extracts, the methanol extracts
reported by Chand et al., who screened various of E. mysorensis, B. neilgherrense, P. pallida,
solvent extracts for antioxidant properties [36]. The and D. barbatulum showed the highest phenolic

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