Studies to understand the effect of Centella asiatica on Aβ(42) aggregation in vitro

Amyloid beta (Aβ) is the major pathological and etiological factor implicated in Alzheimer's disease (AD). Aβ(42) inherently self assembles to form oligomers and fibrils through multifactorial aggregation process. The oligomers and fibrils have toxic effects and may lead to neuronal dysfunction. The inhibition of formation of oligomers and fibrils is a novel strategy in drug development programs for AD. There are limited studies to show to that Centella asiatica has a memory enhancing, anti-acetlylcholinesterase and antioxidant properties. But there are no studies to insight whether C. asiatica prevents Aβ fibrils formation from monomers and oligomers and also to understand whether C. asiatica destabilize the preformed fibrils. Our present study focused on, i) whether the C. asiatica leaf aqueous extract prevent the formation of oligomers and aggregates from monomer? (Phase I: Aβ(42) + extract co –incubation), ii) Whether the C. asiatica aqueous extract prevent the formation of fibrils from oligomers (Phase II- extract added after oligomers formation) and iii) whether the aqueous extract dis-aggregates the pre-formed fibrils (Phase III - aqueous extract added to matured fibrils and incubated for 8 days). The aggregation kinetics was studied using thioflavin-T assay and Transmission Electron Microscopy (TEM).

The results showed that C. asiatica aqueous extract could not able to inhibit the Aβ aggregation both from monomer and oligomers and also could not able to dis-integrate the preformed fibrils. These intriguing results are discussed.