Inlife offers evening primrose oil encapsulated in liquid-filled capsules. Advantages of liquid-filled capsules over soft gels. One of the main advantages of liquids is that they are absorbed directly by the body without going through a break down stages. Active ingredients in liquid form should, therefore, be absorbed faster than in solid form. The evening primrose is a plant of the Onagraceae family, which grows in wild. The flower contains several hundreds of tiny brown seeds. 12 to 30% of oil is extracted from the seeds. Fatty oil is obtained from the seeds of Oenothera biennis by cold pressure. For centuries, evening primrose oil has been trusted to provide nutritional support for women.