What year was the aspirin invented by Charles Gerhardt?

Salicylic acid was also isolated from the herb meadowsweet (Filipendula ulmaria, formerly classified as Spiraea ulmaria) by German researchers in 1839. While their extract was somewhat effective, it also caused digestive problems such as gastric irritation and bleeding and diarrhea, and even death when consumed in high doses. In 1853, a French chemist named Charles Frederic Gerhardt neutralized salicylic acid by buffering it with sodium (sodium salicylate) and acetyl chloride, creating acetosalicylic anhydride. Gerhardt's product worked, but he had no desire to market it and abandoned his discovery. In 1897, researcher Arthur Eichengrün and Felix Hoffmann, a research assistant at Friedrich Bayer & Co. in Germany, derived one of the hydroxyl functional groups in salicylic acid with an acetyl group (forming acetylsalicylic acid, an acetyl ester). This thereby greatly reduced the negative effects caused by the free phenolic group of salicylic acid. When in the body, the ester (aspirin) is hydrolyzed to free the active drug. This was the first synthetic drug, not a copy of something that existed in nature, and the start of the pharmaceuticals industry.