Hot water pressure assisted extraction and chemical analysis of roselle (Hibiscus Sabdariffa L.)

Abstract

Roselle (Hibiscus Sabdariffa L.) is a valuable herbal material due to its natural colorants (mainly Delphinidin), phenolic compounds (chlorogenic acid, protocatechuic acid etc.), vitamins and other substances that provide pharmacological effects [1]. Roselle is known to regulate lipid metabolism [2], reduce hypertension [3] and take role in apoptosis [4]. Different procedures and different solvents have been implemented in extraction of roselle material [5]. Less polar solvents are known to extract less polar compounds (such as polyphenols, phenolic acids, flavonoids, anthocianins etc.) with greater recovery. Some disadvantages when preparing end product as additional steps of extract preparation (vaporization, preparative cleaning etc.) are brought in by such solvents. Water is one of the very few green solvents. It provides different dissolvation abilities at different temperatures. Such effect is caused by change of dielectric constant of water when temperature changes [6]. Classical extraction procedure is limited to only 100oC (boiling temperature of water), but boiling temperature can be increased by increasing pressure in extraction reservoir. Hot water pressure assisted extraction provides a possibility to increase temperature up to 374 oC (supercritical temperature of water) if the pressure is sufficient. Hot water pressure assisted extraction was performed at 4 bar pressure that allowed reaching of 144 oC temperature. Milled raw material (fraction of 0.02-1.2 mm) of roselle was used during procedure [...]