Simultaneous extraction of crocin and geniposide from gardenia fruits (Gardenia jasminoides Ellis) by probe-type ultrasound-assisted natural deep eutectic solvents and their inhibition effects on low density lipoprotein oxidation

Abstract

The simultaneous extraction of crocin and geniposide from gardenia fruits (Gardenia jasminoides Ellis) was performed by integrating natural deep eutectic solvents (NADES) and ultrasound-assisted extraction (UAE). Among the eight kinds of NADES screened, choline chloride-1,2-propylene glycol was the most suitable extractant. The probe-type ultrasound-assisted NADES extraction system (pr-UAE-NADES) demonstrated higher extraction efficiency compared with plate-type ultrasound-assisted NADES extraction system (pl-UAE-NADES). Orthogonal experimental design and a modified multi-index synthetic weighted scoring method were adopted to optimize pr-UAE-NADES extraction process. The optimal extraction conditions that had a maximum synthetic weighted score of 29.46 were determined to be 25 °C for extraction temperature, 600 W for ultrasonic power, 20 min for extraction time, and 25% (w/w) for water content in NADES, leading to the maximum yields (7.39 ± 0.20 mg/g and 57.99 ± 0.91 mg/g, respectively) of crocin and geniposide. Thirty-three compounds including iridoids, carotenoids, phenolic acids, flavonoids, and triterpenes in the NADES extract were identified by LC-Q-TOF-MS² coupled with a feature-based molecular networking workflow. The kinetics evaluation of the conjugated dienes generation on Cu²⁺-induced low density lipoprotein (LDL) oxidation via the four-parameter logistic regression model showed that crocin increased the lag time of LDL oxidation in a concentration-dependent manner (15 μg/mL, 30 μg/mL, 45 μg/mL) by 12.66%, 35.44%, and 73.42%, respectively. The quantitative determination for fluorescence properties alteration of the apolipoprotein B-100 exhibited that crocin effectively inhibited the fluorescence quenching of tryptophan residues and the modification of lysine residues caused by reactive aldehydes and malondialdehydes. The pr-UAE-NADES showed significant efficiency toward the simultaneous extraction of crocin and geniposide from gardenia fruits. And this study demonstrates the potential utility of gardenia fruits in developing anti-atherogenic functional food.

Keywords: Gardenia fruits; Low-density lipoprotein oxidation; Modified multi-index synthetic weighted scoring method; Molecular networking; Natural deep eutectic solvents; Ultrasound-assisted extraction.

Graphical abstract

Fig. 1

FT-IR spectra of CC-PG, BE-PG, and their constituents (a), chemical structures of CC and BE (b), the effect of NADES types on crocin yields (c) and geniposide yields (d). The different letters show significant differences between groups (P < 0.01) by using Tukey’s test.

Fig. 2

Comparisons of the extraction effects on pl-UAE (pl) and pr-UAE (pr) integrated with NADES (CC-PG) of different water content (0%, 25%, 40%, w/w) at different SS ratios (1:20, 1:30, 1:40, g/mL): crocin yields (a) and geniposide yields (b). The different letters show significant differences between groups (P < 0.01) by using Tukey’s test.

Fig. 3

Single-factor experiments results of pr-UAE-NADES: effects of extraction temperatures (a, e), ultrasonic powers (b, f), ultrasonic extraction time (c, g), and water contents of NADES (CC-PG) (d, h) on crocin yields and geniposide yields, respectively. The different letters show significant differences between groups (P < 0.01) by using Tukey’s test.

Fig. 4

Scanning electron microscopy (SEM) images of dried gardenia fruits tissues used for different extraction procedures: without treatment (a), ethanol (60 %) based CHE (b), pl-UAE (c), and pr-UAE (d); CC-PG (25%) based CHE (e), pl-UAE (f), and pr-UAE (g).

Fig. 5

HPLC chromatograms: G1 (a) at 240 nm and G2 (b) at 440 nm.

Fig. 6

Molecular network based on LC-MS² spectra of G1 (green) and G2 (pink) and chemical structures of trans-crocin, cis-crocin, geniposide, and 6′'-O-p-coumaroylgenipin gentiobioside with their extracted ion chromatograms. Node text indicates the m/z of the precursor ion. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 7

The inhibition efficiency of crocin and geniposide on LDL oxidation: Conjugated dienes (CD) evolution (a), Trp fluorescence quenching (b), Lys residue oxidatively modified by reactive aldehydes (c) and malondialdehyde (d). C1: 15 μg/mL Crocin; C2: 30 μg/mL Crocin; C3: 45 μg/mL Crocin; G: 45 μg/mL geniposide. The different letters show significant differences between groups (P < 0.01) by using Tukey’s test.