Withaferin A — The Proteostasis Modulator
Withaferin A is a highly active withanolide derived from Ashwagandha (Withania somnifera) with potent anti-inflammatory, anti-tumor, and proteostasis-enhancing properties. In longevity research, it is of interest for its ability to clear misfolded proteins, reduce oxidative stress, and extend lifespan in model organisms like Drosophila.
Mechanism of Action
Withaferin A is a steroidal lactone that modulates proteostasis and cellular stress responses. It acts as a potent inhibitor of NF-κB, suppressing pro-inflammatory cytokine production. Additionally, it binds to and inhibits vimentin, disrupting intermediate filament networks, and promotes the clearance of misfolded proteins by upregulating heat shock proteins (such as HSP70) and activating the proteasome. In preclinical models, it has also been shown to activate SIRT3, reducing oxidative stress and mitigating fibrosis.
Human Trial Evidence
No published human longevity trials. Animal/in-vitro evidence only. A Phase I trial has evaluated its safety in patients with advanced osteosarcoma, demonstrating good tolerability at high doses, but efficacy for aging or lifespan extension in humans has not been studied.
Dosing Protocol
In a Phase I trial for advanced osteosarcoma, doses up to 4,800 mg of Ashwagandha extract (containing 216 mg of withaferin A) per day were well tolerated. For general supplementation, standard Ashwagandha extracts are typically dosed at 300–600 mg daily, though the specific withaferin A content varies widely. Optimal dosing for longevity purposes in humans remains unestablished.
Safety & Contraindications
Generally well tolerated in clinical trials at studied doses, though high doses may cause mild gastrointestinal distress. Due to its immunomodulatory and anti-angiogenic properties, it should be used with caution in individuals with autoimmune conditions or those taking immunosuppressants. Safety in pregnancy and lactation is not established.