L-Ergothioneine is a high-purity active ingredient supplied as a white to off-white powder, with an HPLC assay specification of 98.0–102.0%. L-Ergothioneine is a naturally occurring amino acid derivative recognised for its antioxidant properties and its role in cellular protection against oxidative stress. Its high purity makes it suitable for premium nutraceutical formulations targeting healthy ageing and antioxidant support.