Effect of the spray and freeze dryers on the bioactive compounds of olive leaf aqueous extract by chemometrics of HCA and PCA

Abstract

Olive leaf extract contains significant amounts of valuable compounds such as Oleuropein and phenolic compounds. The study aimed to introduce a proper method for drying olive leaf extract to increase its value in terms of valuable compounds with antioxidant properties and the correlation among all parameters. Extraction of olive leaf (Mary cultivar, Fars province) was performed using water and ultrasound device and the extract was condensing with two freeze-drying and spray drying methods, and some features were measured as follows: total tannin content, antioxidant activity and inhibitory strength of 50% using the DPPH method, total phenol content using Folin Ciocalteu colorimetric method, total flavonoid by aluminum chloride colorimetric method, and polyphenol compounds using HPLC in olive leaf extract samples. The results showed that the dried extract with freeze-drying had the highest total phenolic content 446.63 ± 7.6 (mg gallic acid per gram dry matter) and the highest antioxidant activity of 96.57 ± 0.19%, inhibitory effect of 0.44 ± 0.32 μg/ml, tannin content of 128.71 ± 0.26 mg of gallic acid per g of dry matter and total flavonoid 396.43 ± 0.25 mg of quercetin per gram of dry matter were seen in the dried extract with spray drying. Evaluation of the type and amount of bioactive compounds in three types of extracts (solution and condensate extracts) by principal components analysis and agglomerative hierarchical clustering (AHC) showed that the use of spray drying has been effective in maintaining the amount of unstable polyphenolic and bioactive compounds.