Kalanchoe crenata Haw. (Crassulacea) Decreases Hippocampal Neuron Loss and Improves Memory and Executive Function in Aged Rats: Implications for Anti-Inflammatory and Antioxidant Mechanisms.

Introduction: Alzheimer's disease is a neurodegenerative disease that alters learning and memory processes. Kalanchoe crenata (Crassulaceae) has long been used in Cameroonian traditional medicine to treat hypertension, malaria, and dementia. The present study aims to evaluate the anti-amnesic effect of an aqueous extract of K. crenata in D-galactose-treated rats and possible mechanisms of action.

Methods: Memory impairment was induced in rats by subcutaneous injection of D-galactose (350 mg/kg) once daily for 30 days. At the end of the procedure, the animals were assessed for memory impairment using Morris water maze and object recognition tasks. Animals with memory impairment were divided into six groups of eight rats each and treated once daily for 24 days as follows: the negative control group received per os distilled water (10 mL/kg); the positive control group received donepezil (2 mg/kg, p.o.); and three test groups received the extract of K. crenata (62, 124, and 248 mg/kg, p.o.). A group of eight rats was added and served as a control group. After completion of the procedure, the memory deficit in rats was reassessed by the object recognition test on Day 15 of the treatment, the Morris water maze test on Day 18, and the open-field test on Day 24. At the end of behavioral experiments, the animals were sacrificed and some biochemical parameters in the hippocampus were estimated. In addition, histological analysis of the hippocampus was performed.

Results: K. crenata significantly decreased the time to reach the platform and increased the time spent in the target quadrant of the Morris water maze. It also increased the discrimination index during the object recognition test. The extract significantly reversed D-galactose-induced oxidative stress and inflammation. This was confirmed by the attenuation of neuronal loss.

Conclusion: These findings suggest that K. crenata extract possesses an anti-amnesic-like effect probably mediated by antioxidant and anti-inflammatory mechanisms.