Developmental stages influence in vivo antimalarial activity of aerial part extracts of Schkuhria pinnata.

ETHNOPHARMACOLOGICAL RELEVANCE: Malaria remains a dire health challenge, particularly in sub-Saharan Africa. In Uganda, it is the most ordinary condition in hospital admission and outpatient care. The country's meager health services compel malaria patients to use herbal remedies such as Schkuhria pinnata (Lam.) Kuntze ex Thell (Asteraceae). Although in vivo studies tested the antimalarial activity of S. pinnata extracts, plant developmental stages and their effect at different doses remain unknown. AIM OF THE STUDY: This study aims to determine the effect of the plant developmental stage on the antimalarial activity of S. pinnata in mice and to document the acute oral toxicity profile. METHODS: Seeds of S. pinnata were grown, and aerial parts of each developmental stage were harvested. Extraction was done by maceration in 70% methanol. The antimalarial activity was evaluated using chloroquine-sensitive Plasmodium berghei on swiss albino mice, in a chemosuppressive test, at 150, 350, and 700 mg/kg, p.o. Standard drugs used were artemether-lumefantrine (0.57 + 3.43) mg/kg and chloroquine (10 mg/kg) as positive controls. Distilled water at 1 mL/100g was used as a negative control. The Lorke method was adopted to determine the acute toxicity of extracts. RESULTS: The flowering stage extract had a maximum suppression of parasitemia at 700 mg/kg (68.83 ± 4.49%). Extract at other developmental stages also significantly suppressed the parasitemia (in the ascending order) fruiting (50.71 ± 1.87%), budding (54.92 ± 7.56%), vegetative (55.39 ± 2.01%) compared to the negative control (24.7 ± 2.7%), p < 0.05. Extracts from all developmental stages increased survival time, with the flowering stage having the highest survival time at 20.33 ± 0.88 days. All extracts had an LD50 of 2157 mg/kg, implying that extracts are safe at lower doses. CONCLUSION: Together, our findings revealed that the S. pinnata extracts at the flowering stage had superior antimalarial activity compared to other plant developmental stages. Extracts from all developmental stages have demonstrated a dose-dependent suppression of malarial parasites and increased survival time with an LD50 of 2157 mg/kg. Thus, for better antimalarial activity, local communities could consider harvesting S. pinnata at the flowering stage. Further studies are needed to isolate pure compounds from S. pinnata and determine their antimalarial activity.

Genetic diversity of aflatoxin-producing Aspergillus flavus isolated from selected groundnut growing agro-ecological zones of Uganda.

BACKGROUND: Groundnut pre- and post-harvest contamination is commonly caused by fungi from the Genus Aspergillus. Aspergillus flavus is the most important of these fungi. It belongs to section Flavi; a group consisting of aflatoxigenic (A. flavus, A. parasiticus and A. nomius) and non-aflatoxigenic (A. oryzae, A. sojae and A. tamarii) fungi. Aflatoxins are food-borne toxic secondary metabolites of Aspergillus species associated with severe hepatic carcinoma and children stuntedness. Despite the well-known public health significance of aflatoxicosis, there is a paucity of information about the prevalence, genetic diversity and population structure of A. flavus in different groundnut growing agro-ecological zones of Uganda. This cross-sectional study was therefore conducted to fill this knowledge gap. RESULTS: The overall pre- and post-harvest groundnut contamination rates with A. flavus were 30.0 and 39.2% respectively. Pre- and post-harvest groundnut contamination rates with A. flavus across AEZs were; 2.5 and 50.0%; (West Nile), 55.0 and 35.0% (Lake Kyoga Basin) and 32.5 and 32.5% (Lake Victoria Basin) respectively. There was no significant difference (χ2 = 2, p = 0.157) in overall pre- and post-harvest groundnut contamination rates with A. flavus and similarly no significant difference (χ2 = 6, p = 0.199) was observed in the pre- and post-harvest contamination of groundnut with A. flavus across the three AEZs. The LKB had the highest incidence of aflatoxin-producing Aspergillus isolates while WN had no single Aspergillus isolate with aflatoxin-producing potential. Aspergillus isolates from the pre-harvest groundnut samples had insignificantly higher incidence of aflatoxin production (χ2 = 2.667, p = 0.264) than those from the post-harvest groundnut samples. Overall, A. flavus isolates exhibited moderate level (92%, p = 0.02) of genetic diversity across the three AEZs and low level (8%, p = 0.05) of genetic diversity within the individual AEZs. There was a weak positive correlation (r = 0.1241, p = 0.045) between genetic distance and geographic distance among A. flavus populations in the LKB, suggesting that genetic differentiation in the LKB population might be associated to geographic distance. A very weak positive correlation existed between genetic variation and geographic location in the entire study area (r = 0.01, p = 0.471), LVB farming system (r = 0.0141, p = 0.412) and WN farming system (r = 0.02, p = 0.478). Hierarchical clustering using the unweighted pair group method with arithmetic means (UPGMA) revealed two main clusters of genetically similar A. flavus isolates. CONCLUSIONS: These findings provide evidence that genetic differentiation in A. flavus populations is independent of geographic distance. This information can be valuable in the development of a suitable biocontrol management strategy of aflatoxin-producing A. flavus.

In vitro regeneration of Ugandan passion fruit cultivars from leaf discs.

OBJECTIVE: Passion fruit improvement efforts by conventional breeding have had limited success calling for research into alternative approaches such as tissue culture and genetic engineering. An efficient and reproducible regeneration system is a prerequisite for successful genetic engineering. Currently, there is no reliable regeneration system for Uganda's passion fruit varieties owing to the high heterogeneity of the Passiflora genus. Therefore, this study aimed at establishing an efficient and reproducible regeneration system for Uganda's Passiflora edulis f. flavicarpa (yellow passion fruit) and Passiflora edulis f. edulis (purple passion fruit) for routine utilization with an ultimate goal of improving its agronomic value. RESULTS: The study successfully induced shoots by both direct and indirect organogenesis for the yellow passion fruit variety. Highest shoot induction frequency (14.85%) was achieved on 8.9 µM BAP while 7.9 µM BAP did not initiate any shoots. Optimal shoot elongation and rooting was achieved on 0.44 µM BAP and 5.37 µM α-naphthaleneacetic (NAA) respectively. Rooted yellow passion fruit plantlets were successfully weaned with over 65% survival rates. It took approximately 6 months to produce a weaned healthy passion fruit plant. The purple passion fruit variety proved to be recalcitrant to tissue culture with no successful shoot or callus induction.