Herb Pharm - Horse Chestnut Extract - 1 oz. (29.6ml) Herb Pharm Horse Chestnut Extract. Herb Pharm prepare their Horse Chestnut Extract from the seeds of Aesculus hippocastanum trees which are Certified Organically grown or Custom Wildcrafted in their natural wild habitat and are never fumigated or irradiated. To assure optimal extraction of Horse Chestnut's bioactive compounds, the seeds are hand-harvested in late summer, are carefully shade-dried, and are then thoroughly extracted.