Optimum Parameters for Extracting Three Kinds of Carotenoids from Pepper Leaves by Response Surface Methodology

Nenghui Li,Wangxiong Li,Feng Gao,Jianming Xie,Jing Li,Jing Zhang,Tianhang Niu,Dongxia Ding,Emily Patience Bakpa,Yufeng Ma,Cheng Wang

doi:10.3390/separations8090134

Abstract

To determine the optimum parameters for extracting three carotenoids including zeaxanthin, lutein epoxide, and violaxanthin from pepper leaves by response surface methodology (RSM), a solvent of acetone and ethyl acetate (1:2) was used to extract carotenoids with four independent factors: ultrasound time (20–60 min); ratio of sample to solvent (1:12–1:4); saponification time (10–50 min); and concentration of saponification solution (KOH–methanol) (10–30%). A second-order polynomial model produced a satisfactory fitting of the experimental data with regard to zeaxanthin (R2 = 75.95%, p < 0.0197), lutein epoxide (R2 = 90.24%, p < 0.0001), and violaxanthin (R2 = 73.84%, p < 0.0809) content. The optimum joint extraction conditions of zeaxanthin, lutein epoxide, and violaxanthin were 40 min, 1:8, 32 min, and 20%, respectively. The optimal predicted contents for zeaxanthin (0.823022 µg/g DW), lutein epoxide (4.03684 µg/g dry; DW—dry weight), and violaxanthin (16.1972 µg/g DW) in extraction had little difference with the actual experimental values obtained under the optimum extraction conditions for each response: zeaxanthin (0.8118 µg/g DW), lutein epoxide (3.9497 µg/g DW), and violaxanthin (16.1590 µg/g DW), which provides a theoretical basis and method for cultivating new varieties at low temperatures and weak light resistance.

Highlights

Pepper (Solanaceae: Capsicum annuum L.) is the most vital off-season vegetable cultivated in greenhouses in northwestern China [1,2]
The results showed that acetone and ethyl acetate were the best two solvents for extraction, and further study of the different ratios (3:1, 2:1, 1:1, 1:2, and 1:3) of the two were performed, where the results indicated that acetone:ethyl acetate = 2:1 was the best choice
Zeaxanthin and violaxanthin are key precursors of light-harvesting carotenoids involved in the photoprotective xanthophyll cycle, while lutein epoxide is unique to photosynthetic eukaryotes [39,40]; they are absolutely necessary in biological activities

Summary

Introduction

Pepper (Solanaceae: Capsicum annuum L.) is the most vital off-season vegetable cultivated in greenhouses in northwestern China [1,2]. As one of the most favored vegetables, with its fruit mainly valued as a food seasoning, pepper fruit is an excellent source of natural pigments, including neoflavin, cyanin, monoepoxy zeaxanthin, lutein, zeaxanthin, lutein epoxide, lycopene, octet lycopene, α-carotene, and β-carotene [3], which are responsible for the fruit’s color that ranges from yellow, to orange, to red [4]. Numerous studies on carotenoids are mainly in relation to food science and chemistry. Most of these studies focused on changes in the concentrations and quantities of carotenoids in fruits or vegetables, such as red pepper [3], citrus [9], durian [10], red navel orange [11], goldenberry [12], and mango [13] during maturity, storage, and processing cycles.

Methods

Results

Discussion

Conclusion