Abstract: A process for the preparation of protoescigenin by hydrolysis of escin isolated from Aesculus hippocastanum. The process includes the following steps: a two-step hydrolysis first under acidic and then basic conditions, enrichment of the crude mixture of sapogenins with protoescigenin, an isolation of the mixture of sapogenins in a solid form, and a purification of the obtained solid and isolation of high purity protoescigenin. The invention also relates to protoescigenin monohydrate in a crystalline form and the preparation thereof. Protoescigenin is a polyhydroxy aglycone, which can be used as a synthon in the chemical modifications of naturally occurring saponins.