| dc.description.abstract | Opportunistic infections caused by fungi have been on the rise and are a threat to the lives of
the immunocompromised individuals. The few antifungal drugs available are either toxic or
have adverse side effects, necessitating search for an alternative agent. This present study was
conducted to determine the antifungal activity, cytotoxicity and the phytochemical
composition of the Kenyan species of Gladiolus and Dierama (Iridaceae). Aerial and bulb
crude aqueous and organic extracts (DCM:MeOH) were tested against Candida albicans,
Aspergillus niger and Cryptococcus neoformans by disc diffusion method while cytotoxicity
was determined using freshly-hatched brine shrimp (nauplii), Artemia salina. Semi-purified
fractions of bulbs were also tested against the three fungi. Phytochemical screening, Thin
Layer Chromatography and column chromatographic bioassay guided fractionation of bulbs
and aerial parts were conducted using standard procedures. Anatomical features of bulbs and
leaves were evaluated to establish characteristics to differentiate between the species.
Organic extracts were found to be more active than aqueous crude extracts while bulbs from
both extracts showed higher activity than the aerial parts. Bulbs of Dierama cupuliflorum,
Gladiolus watsonoides and G. goetzenii all showed a minimum inhibitory concentration value
of 0.3907mg/ml when tested against C. albicans implying their strong activity against this
fungus. Other than G. ukambanensis, bulb extracts of all the other plants had weak activity
(>0.625mg/ml) against A. niger while only bulbs of G. watsonoides and G. goetzenii showed
weak activity (>0.625mg/ml) against C. neoformans. Semi-purified fractions from ethyl
acetate, methanol or their mixtures showed the highest activity whereas fractions from
hexane and dichloromethane were either inactive or had little activity. When compared to the
activity of the commercially used drugs, two–way ANOVA revealed that bulbs of D.
cupuliflorum, G. watsonoides, G. goetzenii and G. newii had activities not significantly
different (P>0.05) to that of amphotericin B at concentrations 5mg/100µl, 2.5mg/100µl and 1.25mg/100µl when tested against C. albicans. G. watsonoides and G. goetzenii bulbs had
activity significantly higher (F,8,72=4.56, P<0.05) than nystatin at 5mg/100µl. when tested
against C. neoformans. All the drugs had significantly higher activity than the plant extracts
when tested against A. niger. Cytotoxic activities revealed that all the bulb extracts were toxic
to the newly hatched shrimps with LD50 value <500µg/ml except those of G. ukambanensis
which showed weak toxicity with LD50 value >500µg/ml. Similarly, all aerial extracts were
toxic except those of G. ukambanensis which were non toxic with LD50 value >1000µg/ml.
The phytochemicals screened such as alkaloids, flavonoids, saponins, terpenoids, glycosides,
anthraquinones, tannins were detected in the bulbs than in the aerials. Bulbs of D
.cupuliflorum and G. watsonoides tested positive for seven of the eight tested major classes of
phytochemicals followed by G. goetzenii and G. newii in that order. G. ukambanensis had
only three of the tested phytochemicals. There was a linear correlation between bioactivity,
cytotoxicity and richness of phytochemicals. Anatomical features of bulbs were found to be
different and the description was done based on the tunic texture and colour and stack
formation of the bulbs. These may be of value in identification of these plants during dry
periods when the aerial parts are absent. This study has shown the potential of these plants as
source of leads for antifungal drug development towards combating emerging antifungal
resistance to conventional drugs. Further purification and bioassay analyses of these plants
are recommended to ascertain the antifungal and cytotoxic principles. Due to their possible
economic value conservation measures may be necessary to control their exploitation. | en_US |
