Exploring new antimicrobial
and cytotoxic drugs has been one of
the most active areas of research.
Rhamnus purpurea
(Edgew.) buckthorn (
Rhamnaceae
) is a wild shrub
traditionally used in Pakistan for the treatment of various ailments
including cancer and infectious diseases. The aim of this study is
to find novel antimicrobial and cytotoxic agents of plant origin.
The crude methanol extract and full range of fractions of
R. purpurea
leaves were screened for the said activities
using
in vitro
antimicrobial, antioxidant, and cytotoxic
models following standard protocols. The antimicrobial activity was
evaluated using the agar well diffusion method, while the antioxidant
activity was assessed with 1,1-diphenyl-2-picryl hydrazyl (DPPH) and
ferric reducing antioxidant power (FRAP) assays. The cytotoxic effect
was investigated against the human cancer cell lines i.e. Caco-2 (gut),
A549 (lung), HepG2 (liver), and MDA-MB-231 (breast) by MTS assay.
In addition, toxicity studies were conducted on renal and alveolar
primary epithelial cells (HRPTEpiC and HPAEpiC, respectively). Phytochemical
investigation showed the presence of secondary metabolites such as
alkaloids, saponins, tannins, glycosides, phenols, carbohydrates,
proteins, and flavonoids. The
n
-hexane and chloroform
fractions showed significant activity against
Staphylococcus
aureus
(MIC 0.60 and 0.68 mg/mL, respectively),
Salmonella typhi
(MIC 0.48 and 0.45 mg/mL, respectively),
and
Bacillus subtilis
(MIC 0.54 and
0.76 mg/mL, respectively). Among fungal strains, crude methanol and
chloroform fractions exhibited significant activity against
Fusarium solani
(MIC 0.53 and 0.44 mg/mL, respectively)
and
Aspergillus niger
(MIC 0.47 and
0.42 mg/mL, respectively). The crude methanol,
n
-hexane
and chloroform fractions revealed the highest antioxidant activity
at 1000 μg/mL, compared to that of ascorbic acid. The
n
-hexane fraction showed a significant cytotoxic effect
against Caco-2, A549, and HepG2 cell lines with IC
50
values
of 5.65 ± 0.88, 5.50 ± 0.90, and 4.95 ± 1.0 μg/mL,
respectively. Similarly, the chloroform fraction depicted significant
activity against Caco-2, A549, and HepG2 cell lines with IC
50
values of 4.55 ± 1.25, 4.65 ± 1.55, and 2.85 ± 0.98
μg/mL, respectively. The crude methanol extract and almost all
fractions exhibited the highest selectivity index (>2.0) for Caco-2,
A549, and HepG2 cancer cell lines, providing safety data for this
study. The results showed that
R. purpurea
leaves have excellent antimicrobial, antioxidant, and cytotoxic
potential and warrant further studies to search for novel compounds
for the said activities.
