Abstract:
Introduction: Coleus lanuginosus and Microglossa
pyrifolia are woody perennial herbs that are widely
cultivated in Africa, Asia, and Australia. The use of
crude extracts from leaves, stems and roots of
these plants has been reported in traditional
folklore medicine as a remedy for varied diseases.
This study sought to investigate the phytochemical
composition and evaluate the antimicrobial
activities of the stem and leaf extracts of Coleus
lanuginosus and Microglossa pyrifolia. Methods:
the stem and leaf of both plants were collected
from eastern Kenya, air-dried, and crushed into
powder, and the crude extract was obtained using
Soxhlet apparatus with aqueous and methanolic
solvents. The antibacterial and antifungal activity
was evaluated against gram-positive bacteria
(Bacillus subtilis, Staphylococcus aureus) and
gram-negative bacteria (Pseudomonas aeruginosa,
Escherichia coli) and the fungus Candida albicans.
Antibacterial
and antifungal activity were
evaluated by the disc diffusion method. The
minimum inhibitory concentration (MIC) of the
extracts was also determined. Results: qualitative
and quantitative phytochemical screening was
done on the two plants to establish the presence of
biologically important secondary metabolites. Both
methanolic and aqueous crude extracts of C.
lanuginosus and M. pyrifolia demonstrated to
possess antibacterial and antifungal activity
against the selected microbes. The extracts
showed minimum inhibitory concentration (MIC)
activity against Bacillus subtilis, Staphylococcus
aureus Pseudomonas aeruginosa and Escherichia
coli
ranging
from 6.25mg-50mg/kg with
M. pyrifera leaf extract resulting in the highest
zones of inhibition. The phytochemical constituents
identified were flavonoids, alkaloids, glycosides,
phenols, saponins, steroids, and terpenoids, with
alkaloids, glycosides, saponins, and steroids being
the most abundant. Gas chromatography-mass
spectrometry (GC-MS) analysis led to the
identification of fifty-nine compounds with all the
extracts containing at least two or more long-chain
unsaturated fatty acids which have been linked to
antimicrobial activity. Conclusion: in conclusion, C.
lanuginosus and M. pyrifolia extracts have great
potential as a source of novel antimicrobial and
antifungal agents and possess a wide range of
bioactive phytochemical compounds with the
potential for ethnomedicinal use.
