Ethno pharmacological relevance: Chungtia villagers of
Nagaland, India, have a strong reliance on plants as medicines. Previous
studies have shown that 31 Chungtia medicinal plants (and parts therein)
used customarily for skin related treatments possess
antimicrobial properties against skin pathogens, strongly supporting the
use of these plants by the Chungtia villagers. Five plants,
namely Albizia lucidior, Begonia picta, Cassia floribunda, Holboellia
latifolia and Maesa indica have no previous studies on their
antimicrobial
properties, while Prunus persica has only antimicrobial activity
reported on its fruit, with no reports on its roots, which
are used by the Chungtia villagers. The aim of the study was to
investigate these six plants for their antimicrobial properties against
dermatologically relevant pathogens and undertake phytochemical analysis
of the most active species, Prunus persica.
Materials and Methods: 70% aqueous ethanoic extracts were
prepared of leaves of B. picta, C. floribunda, H. latifolia and M.
indica and roots of A. lucidior and P. persica. The crude extract of P.
persica was successively partitioned between water and n-hexane,
dichloromethane (DCM) and ethyl acetate (EtOAc). TLC bioautography
guided fractionation using column chromatography of
the n-hexane and EtOAc partition afforded five compounds. The structures
of the compounds were elucidated by 1D and 2D NMR
spectroscopic techniques and comparison with published data. The crude
extract and partitioned fractions of P. persica as well as the
isolated compounds were screened against antibiotic sensitive and
resistant strains of Staphylococcus aureus and Escherichia coli as
well as antibiotic sensitive Pseudomonas aeruginosa, Streptococcus
pyogenes, Salmonella typhimurium and the fungus C. albicans using
the MTT (3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide)
microtitre dilution and disc diffusion assay methods.
Results: All of the plant aqueous ethanolic extracts exhibited
antibacterial activity against at least two of the tested
microorganism.
The most noteworthy activity was shown by P. persica root extract
against antibiotic sensitive as well as resistant (methicillin
resistant [MRSA] and multi drug resistant [MDRSA]) strains of S. aureus
(0.156mg/mL for all tested strains). None of the plants
were active against the fungus C. albicans. This is the first report of
antibacterial activity for all of these plants except for P. persica of
which the fruit has been previously reported to be anti bacterially
active. The partitioned fractions of P.persica showed antibacterial
activity, with the highest antimicrobial activity for the EtOAc fraction
with MIC 312μg/mL (susceptible as well as resistant strains
of S.aureus), followed by n-hexane MIC 625μg/mL (susceptible S. aureus)
and MIC 312μg/mL (MRSA and MDRSA). Bioassay guided
fractionation of the EtOAc partition resulted in isolation of
ent-epiafzelechin-(2α→O→7, 4α→8)-(-)-ent-afzelechin (1), afzelechin
(2), Caffeic acid phenylethyl ester (3) and Gallic acid (4). GC-MS
analysis of the n-hexane extract showed the presence of the
antibacterial
compounds palmitic acid, linoleic acid and oleic acid. Bioassay guided
fractionation of the n-hexane partition resulted in
isolation of three ant bacterially active compounds: α-cyanobenzyl
benzoate (4), MIC 0.78μg/mL for susceptible and resistant S.
aureus strains, MIC 312μg/mL for susceptible and resistant E. coli
strains and MIC 625μg/mL for P. aeruginosa), β-sitosterol (5) MIC
2500μg/mL for susceptible and resistant S. aureus strains and antibiotic
susceptible E. coli, MIC 625μg/mL for antibiotic susceptible
S. typhimurium and MIC 1250μg/mL for antibiotic susceptible P.
aeruginosa) and stigmast-4- en-3-one (6) MIC 156μg/mL for susceptible
and resistant S. aureus strains, MIC 312μg/mL for antibiotic susceptible
E. coli, MIC 625μg/mL for antibiotic susceptible
S. typhimurium and MIC 1250μg/mL for antibiotic susceptible P.
aeruginosa). This is the first report for antibacterial activity for
α-cyanobenzyl benzoate and stigmast-4-en-3-one.
Conclusion: Aqueous ethanolic extracts of six Chungtia
medicinal plants used for skin related ailments were found to have
antibacterial properties against dermatologically relevant bacteria,
supporting their customary uses by Chungtia villagers. Good
antibacterial activity of the EtOAc and n-hexane partitioned fractions
from the P. persica root extract and the isolated compounds
ent-epiafzelechin-(2α→O→7, 4α→8)-(-)-ent-afzelechin, α-cyanobenzyl
benzoate, β-sitosterol and stigmast-4-en-3-one as well as
antibacterially active compounds identified from the GC- MS studies
further supports the customary use of roots of this species in
treating skin related ailments.
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