Department of Biological Scienceshttps://karuspace.karu.ac.ke/handle/20.500.12092/17932024-03-28T15:36:10Z2024-03-28T15:36:10ZANTIBACTERIAL EFFICACY AND SAFETY OF SELECTED KENYAN MEDICINAL PLANTSAbiba, Alfred Ogaohttps://karuspace.karu.ac.ke/handle/20.500.12092/28062023-03-09T00:00:16Z2013-06-01T00:00:00ZANTIBACTERIAL EFFICACY AND SAFETY OF SELECTED KENYAN MEDICINAL PLANTS
Abiba, Alfred Ogao
Many disease-causing organisms have become resistant to conventional antibiotics. The toxicity
and side effects of conventional drugs have also become increasingly unmanageable, while their
costs are prohibitive. It has therefore become necessary to continue searching for alternative
medicines to treat such diseases. The possibility of developing pharmaceutical industries using
local raw materials should be looked into critically so that the cost of drugs can be affordable to
the local people. This study involved screening of various medicinal plants commonly used by
herbal medicine practitioners for bioactive compounds against bacteria. Standard bioassay
methods were employed throughout this study. They included preliminary screening bioassay
against human pathogenic bacteria strains using Agar Disc Diffusion method, Minimum
Inhibitory Concentration (MICs), Minimum Bactericidal Concentration (MBCs), Time kill
kinetics, phytochemical determination methods and one dose in vivo toxicity tests using mice.
Hexane, dichloromethane, acetone and methanol extracts of ten (10) medicinal plants:
Dichrostachyus. cinerea, Combretum molle, Euclea divinorum, Ficus sur, and other five plants
were screened by preliminary bioassay against nine (9) human pathogenic bacteria strains (E.
coli, ATCC 25922 S. aureus ATCC 85923, Pseudomonas aeruginosa NCTC 10662,
Escherichia coli, Shigella flexinery, Pseudomonas aeruginosa, Staphlococcus aureus, Shigella
dysenteriae and Klebsiella hospital isolates) using agar disc diffusion method. Acetone,
methanol extracts of D. cinerea and C. molle showed remarkable inhibitory activity against all
nine human pathogenic bacteria. Acetone and dichloromethane of E. divinorum and F. sur
showed activity against all human pathogenic bacteria except P. aeruginosa and klebsiella. All
extracts of six (6) plants were inactive against the test human pathogenic bacteria. MICs of
acetone and methanol extracts of the four (4) plants D. cinerea, C. molle, and dichloromethane
and acetone extracts of E. divinorum and F. sur were active against the test bacteria. MIC results
showed that acetone and methanol extracts of D. cinerea, and C. molle gave very good low
MICs ranges (0.3-2.5mg/ml), dichloromethane and acetone extracts of E. divinorum and F. sur
gave MICs ranging between 7.5-100mg/ml. MBCs of acetone and methanol extracts of D.
cinerea, and C. molle were as low as 0.3mg/ml while the highest being 5mg/ml. Phytochemical
determination showed that both methanolic and acetone extracts of D. cinerea and C. molle
contained alkaloids, tannins, steroids and triterpenoids, flavone glycones, anthrocyanins and
reducing sugar. Kill kinetics studies of the bioactive organic extracts on the tested bacteria
indicated that acetone extracts of D. cinerea, acetone extracts of C. molle, methanol extracts of
C. molle, methanol extracts of D. cinerea at 4, 6 and 8mg/ml against Staphylococcus aureus
ATCC 85923, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa NCTC 10662,
displayed dose and time dependent rapid kinetics of the bacterial killing. Because the toxicity of
a drug to the bystander host cells could render it unsuitable for therapeutic purposes, the toxicity
of the active plant extracts against the tested bacteria was assessed. The reduced growth rate,
organ weights, white and red blood cells counts, plus increased levels of biochemicals in the
serum in plant extract treated animals relative to that of the controls, indicate that these extracts
contained constituents with toxic effects on them. Such constituents include some of the
phytochemicals present in these extracts. The mineral content may also cause toxicity but this was not
the case with the measured minerals since their levels were below the recommended daily allowance
except for potassium which was 67 to 141 times the recommended daily allowance.
Anti-bacterial efficacy safety of selected Kenya Medicinal Plants
2013-06-01T00:00:00ZEnhancing Tripartite Symbiosis between Soybean, Bradyrhizobia and Arbuscular Mycorrhizal Fungiunder Contrasting Farm Management Practices in Tharaka-Nithi County-KenyaGitonga, Nicholas Mawirahttps://karuspace.karu.ac.ke/handle/20.500.12092/28042023-03-09T00:00:15Z2021-05-01T00:00:00ZEnhancing Tripartite Symbiosis between Soybean, Bradyrhizobia and Arbuscular Mycorrhizal Fungiunder Contrasting Farm Management Practices in Tharaka-Nithi County-Kenya
Gitonga, Nicholas Mawira
Organic farming is gaining popularity as agronomically and environmentally sound
soil management strategy with the potential to enhance soil microbial diversity and
fertility, environmental quality and sustainable crop production. However, the role
of bradyrhizobia and arbuscular mycorrhizal fungi (AMF) in organic farming
systems is poorly understood. Field experiments were carried out to evaluate the
effects of organic farming and bradyrhizobia inoculation on soybean nodulation,
AMF root colonization, growth, production and yield quality. Greenhouse and
laboratory experiments sought to determine the effects of bradyrhizobia and/or AMF
inoculation and dual inoculation in promoting root colonization and nodulation,
determine soil mycorrhizal inoculum potential (MIP), evaluate the abundance and
effectiveness of native bradyrhizobia and determine the morphological and genetic
diversity of native bradyrhizobia isolates under different farm management
practices. Field experimental treatments included native bradyrhizobia, commercial
Bradyrhizobiun japonicum, a mixture of native and commercial Bradyrhizobium
japonicum and control. Promiscuous soybeans varieties SB 19 and SC squire as well
as non-promiscuous Gazelle were used as test plants. All field experiments were
carried out in split-split plot design. In the greenhouse, AMF and bradyrhizobia were
inoculated and dual inoculated on SC squire soybeans. The AMF inoculants used
were Funneliformis mosseae and Rhizophagus irregularis while bacteria involved
commercial bradyrhizobia and native bradyrhizobia. Greenhouse experiments were
set out using completely randomized design. The native bradyrhizobia were isolated
and characterized. Deoxyribonucleic acid (DNA) from nodule isolates was extracted
using Gene Jet DNA extraction kit. Polymerase chain reaction (PCR) targeting 16S
rDNA gene was carried out using universal primers P5-R and P3-F. Polymerase
chain reaction product purification and sequencing was carried out in MacrogenNetherlands. Sequencing was done using the same primers. Non molecular data
obtained was analyzed using analysis of variance (ANOVA). Means that were
significantly different at p< 0.05 were separated using Tukey’s HSD test. Field
experiment results demonstrated significant improvement of soybean nodule dry
weight (NDW), shoot dry weight (SDW) and seed dry weight (SEDW) due to
inoculation. Bradyrhizobia inoculation increased soybean seed yields by between
29-59% of its potential yield. Remarkably, organic farming significantly (p=0.001)
out-performed conventional systems in SDW, NDW, SEDW and AMF root
colonization. Moreover, seed nutrient significantly differed in organic and
conventional farming where, seed nitrogen, phosphorus, potassium and organic
carbon were higher in organic farming. Soybean varieties differed significantly on
SDW, NDW and SEDW, where SC squire performed better compared to SB 19 and
Gazelle. Greenhouse results showed bradyrhizobia and AMF dual inoculation
significantly enhanced AMF root colonization, NDW and SDW compared with
individual bradyrhizobia, AMF or control. Moreover, organic farming significantly
(p=0.001) increased SDW, NDW and AMF root colonization compared to
conventional farming. Organic farming had a significant effect (p = 0.001) on soil
MIP. Based on molecular analysis, isolates were bradyrhizobia and matched with
Bradyrhizobium japonicum among other species. There was little or no genetic
differentiation of isolates with the highest molecular variation (91.12%) within the
populations and 8.88 % among populations. The results demonstrate the importance
of organic farming and dual inoculation in sustainable crop production. The highly
potential native bradyrhizobia isolates (GRPc and GRPk) and exotic AMF should be
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popularized and commercially ultilized by farmers to alleviate declining soil fertility
and increase food production with minimum expenses.
Enhancing Tripartite Symbiosis between Soybean, Bradyrhizobia and Arbuscular Mycorrhizal Fungiunder
2021-05-01T00:00:00Z