Tulbaghia violacea Harv. plant extract affects cell wall synthesis in Aspergillus flavus

AIMS

This study investigates the effect that aqueous extracts of Tulbaghia violacea Harv. harbouring plant saponins, phenolics and tannins have on Aspergillus flavus β-(1,3) glucan and chitin synthesis.

METHODS AND RESULTS

Aspergillus flavus was treated with various subinhibitory concentrations of an aqueous T. violacea plant extract and the β-(1,3) glucan and chitin content was determined together with glucan synthase and chitin synthase production respectively.

CONCLUSIONS

The aqueous extract caused a significant decline (P < 0·05) in β-glucan production in A. flavus in a dose-dependent manner when compared to the untreated sample. Further investigations showed a decrease in β-glucan synthase production as the concentration of the plant extract was increased. A significant reduction in total chitin content corresponding to a decrease in chitin synthase production in the presence of the plant extract was also found.

SIGNIFICANCE AND IMPACT OF THE STUDY

The broad spectrum activity and the efficacy of aqueous T. violacea plant extract on both β-glucan and chitin synthesis may limit the potential of the fungus developing resistance towards it and therefore the extract is an ideal candidate for use as a potential antifungal agent.

The antimosquito properties of extracts from flowering plants in South Africa

Extracts of selected flowering plants, which are considered eco-friendly, are used for the treatment of numerous ailments and vector control worldwide. This has resulted in approximately 25 per cent of currently used drugs being derived from herbal sources. The aqueous and methanolic extracts of twelve plant species, Psidium guajava (pink fruit), Psidium guajava (white fruit), Psidium cattleianum var. cattleianum, Psidium guineense and Psidium X durbanensis, Achyranthes aspera, Alternanthera sessilis, Guilleminea densa, Capparis tomentosa, Leonotis leonurus, Dichrostachys cinerea and Carpobrotus dimidiatus, were tested for insecticidal activity, including larvicidal, adulticidal and repellent activities against the adult female mosquito, Anopheles arabiensis. The extracts of P. guajava (white fruit), C. tomentosa, L. leonurus,D. cinerea, and C. dimidiatus exerted a pronounced inhibitory effect on adult insects, while those of P. guajava (pink fruit), P. X durbanensis, P. cattleianum var. cattleianum, P. guineense, A. aspera, A. sessilis, and G. densa were ineffective and failed to satisfy the criteria set by the World Health Organization. In the tests for repellency against An. arabiensis, all the tested aqueous and methanolic plant extracts except those of A. sessilis repelled 80-100% of mosquitoes. The most effective mosquito repellents were the methanol and aqueous extracts of P. guajava (pink fruit), P. X durbanensis, P. cattleianum var. cattleianum, P. guineense, G. densa,L. leonurus and D. cinerea, which are potential sources of cost effective mosquito repellents to be utilized in malarial endemic areas.

Angiotensin I-converting enzyme inhibitor activity of nutritive plants in KwaZulu-Natal

Traditional herbal remedies still form an integral part of South African culture, hence necessitating reports on the scientific rationale for their uses. Organic and aqueous extracts from 16 nutritive plants found in KwaZulu-Natal, South Africa were screened for angiotensin I-converting enzyme (ACE) inhibitory activity using a fluorometric enzyme assay. A plant was considered to have potential antihypertensive properties if it inhibited the ACE enzyme and thus the conversion of angiotensin I to angiotensin II by greater than 50%. Eight of the 16 plants screened demonstrated ACE inhibitory activity and satisfied these criteria. These eight plants were then subjected to a gelatin salt block test for tannins to show that the ACE inhibitory activities were not due to the presence of tannins, as tannins also inhibit ACE activity. The plants that showed ACE inhibitory activity were Amaranthus dubius, Amaranthus hybridus, Asystasia gangetica, Galinsoga parviflora, Justicia flava, Oxygonum sinuatum, Physalis viscosa, and Tulbaghia violacea. T. violacea in particular shows promise with regards to ACE inhibition as in vivo administration of this extract showed only a 2.2% increase in maximum mean arterial pressure when compared to the 14.5% increase observed in the control group after co-administration with exogenous Ang I.

The in vivo effects of Tulbhagia violacea on blood pressure in a salt-sensitive rat model

AIM OF THE STUDY

The in vivo effects of Tulbhagia violacea on systemic arterial blood pressure and on the renin-angiotensin system in a Dahl salt-sensitive rat model were investigated.

MATERIALS AND METHODS

Animals were treated for 14 days intraperitoneally as follows: Tulbhagia violacea (Tvl) (50mg/kg b.w.), captopril (Cap) (10mg/kg b.w.) or DMSO (Con). Baseline blood pressures were recorded prior to the commencement of the study and biweekly during the experimental period. Urine volume and sodium concentration were measured during the experimental period. On day 15, animals were anaesthetized (sodium thiopentane, 50mg/kg, i.p.), blood samples for aldosterone levels were taken and the kidneys removed for determining AT1a mRNA expression.

RESULTS

Cap and Tvl groups showed significantly reduced AT1a mRNA expressions by 3.11- and 5.03-fold, respectively, when compared to the Con group (p<0.05). When compared to baseline blood pressures (day 0); Cap and Tvl showed reductions in systolic blood pressure (SBP) of 7.76+/-0.41% and 9.12+/-0.31%, respectively (mean% decrease from day 0 to day 14). In contrast, in the Con group the systolic blood pressure increased from day 0 to day 14 by 4.66+/-0.56%. Blood pressure changes in all treated groups differed from Con significantly. Systolic blood pressure decreased with the decrease in AT1a mRNA expressions in these groups. When comparing day 0 to day 14, urine output increased in the Cap and Tvl groups. In the Con group, urinary volume was reduced by day 14 as compared to day 0. Urinary sodium excretion was increased in the treated groups by day 14.

CONCLUSION

It can be concluded that Tulbhagia violacea reduces systemic arterial blood pressure in the Dahl rat by decreasing renal AT1 receptor gene expression and hence modulating sodium and water homeostasis.

Aspects of pollination and floral development in Ficus capensis Thunb. (Moraceae)

A unique obligatory symbiosis exists between Ficus capensis Thunb., and its pollinator, Ceratosolen capensis Grandi. Flowers from both aerial and geocarpic syconia may be pollinated and produce seeds. Females of C. capensis possess specialized mesothoracic pockets in which pollen is transferred from ripening syconia to receptive ones. A second primary sycophile, Sycophaga cyclostigma Waterston, appears to be ineffective in pollination.Several secondary sycophiles oviposit through the syconial wall. Strong sexual dimorphism exists in most sycophilous wasps. All female flowers have the potential to produce either seeds or galls and variation is merely one of gross morphology. Flowering is distinctly asynchronous. Seeds are dispersed by various fruit predators and germinate very easily under warm humid conditions.

A new species of Bulbine (Liliaceae) from Australia

Bulbine alata, a new species, is described together with brief comments on other Australian members of the genus. Illustrations, including scanning electron micrographs of seed surfaces, are presented. A key to the species is provided.