Cassia angustifolia Vahl. plant is used for many therapeutic purposes, for example, in people with constipation, skin diseases, including helminthic and parasitic infections. In our study, we demonstrated an amoebicidal activity of C. angustifolia extract against Acanthamoeba triangularis trophozoite at a micromolar level. Scanning electron microscopy (SEM) images displayed morphological changes in the Acanthamoeba trophozoite, which included the formation of pores in cell membrane and the membrane rupture. In addition to the amoebicidal activity, effects of the extract on surviving trophozoites were observed, which included cyst formation and vacuolization by a microscope and transcriptional expression of Acanthamoeba autophagy in response to the stress by quantitative polymerase chain reaction. Our data showed that the surviving trophozoites were not transformed into cysts and the trophozoite number with enlarged vacuole was not significantly different from that of untreated control. Molecular analysis data demonstrated that the mRNA expression of AcATG genes was slightly changed. Interestingly, AcATG16 decreased significantly at 12 h post treatment, which may indicate a transcriptional regulation by the extract or a balance of intracellular signalling pathways in response to the stress, whereas AcATG3 and AcATG8b remained unchanged. Altogether, these data reveal the anti-Acanthamoeba activity of C. angustifolia extract and the autophagic response in the surviving trophozoites under the plant extract pressure, along with data on the formation of cysts. These represent a promising plant for future drug development. However, further isolation and purification of an active compound and cytotoxicity against human cells are needed, including a study on the autophagic response at the protein level.

Reactivation of sand drift is a common phenomenon in arid areas and needs suitable surface vegetation in association with overstorey trees for better stabilization. Regeneration and survival of Cassia angustifolia seedlings were studied in relation to different adult neighbours and soil water content with a view to developing effective surface vegetation and control of sand drift. Acacia tortilis, Prosopis juliflora and Calligonum polygonoides were the experimental adult neighbours. Observations were recorded at distances of 0–1.0 m (inner canopy [IC] zone), 1.0–1.5 m (outer canopy [OC] zone) and 1.5–2.5 m (outside the canopy [OS] zone) from the neighbours. Seeds and regenerated seedling densities were higher in the C. polygonoides plot than the other two neighbours and the control plots. The density was higher in the OC zone of the C. polygonoides and P. juliflora plots, the OS zone of the A. tortilis plot and the IC zone of the control plot. Both inter- and intraspecific competition resulted in high mortality during July–October in A. tortilis and P. juliflora plots. Seedling survival decreased in February and June, but the density, which was greater in the IC zone, was positively correlated with that in July and with the soil water content (SWC). The ultimate survival of seedlings was higher in the neighbour inclusion than control plots. The soil water content (SWC) was generally higher in the Calligonum polygonoides plot than that in the A. tortilis and P. juliflora plots. With distance from the adult neighbours, the SWC increased in the 25–50 cm and 50–75 cm and decreased in the 0–25 cm soil depth layers. Shoot height and biomass of one-year-old C. angustifolia seedlings were higher in the C. polygonoides plot than in the plots of other neighbours. A negative relative neighbour effect for most of the growth variables suggests that the adult neighbours facilitated regeneration, survival, growth and biomass of C. angustifolia seedlings. C. polygonoides was the best neighbour, with better soil water content at depth and the most positive influence on seedling growth; it is therefore a suitable planting partner for C. angustifolia in promoting the effective stabilization of dunes.