Isolation, Gastroprotective Effects and Untargeted Metabolomics Analysis of Lycium Minutifolium J. Remy (Solanaceae)

Lycium minutifolium J. Remy (Solanaceae) is commonly used as an infusion in traditional medicine to treat stomach pain, meteorism, intestinal disorders, stomach ailments, and other severe problems including prostate cancer and stomach cancer. From the EtOAc extract of L. minutifolium bark five known metabolites were isolated using chromatographic techniques. The gastroprotective effects of the EtOAc fraction and edible infusion extract of the bark were assayed on the hydrochloric acid (HCl)/EtOH induced gastric ulcer model in mice to support the traditional use of the plant. The EtOAc extract and the edible infusion showed gastroprotective effect at dose of 100 mg/kg reducing lesions by 31% and 64%, respectively. The gastroprotective action mechanisms of the edible infusion at a single oral dose of 100 mg/kg were evaluated suggesting that prostaglandins, sulfhydryl groups, and nitric oxide are involved in the mode of gastroprotective action. The UHPLC analysis coupled to high-resolution mass spectrometry of the edible infusion showed the presence of twenty-three compounds. Our results can support the gastroprotective properties of the edible infusion extract, and at least can validate in part, the ethnopharmacological uses of the plant.


Introduction
Peptic ulcer disease refers to a group of ulcerative disorders that occur only in those parts of the digestive tract exposed to acid and pepsin produced by gastric mucosa. Peptic ulcers are associated with fatal complications such as stomach perforation or stomach bleeding that may cause death [1].

Plant Material
Lycium minutifolium J. Remy were collected in 2017 at "Cuesta el gato" (Copiapo, III Región, Chile) and identified by Prof. Dra Gloria Rojas from the Museo de Historia Natural, Santiago-Chile. A voucher specimen (Nº LM120217) is kept at the Natural Product Lab. of the Universidad de Chile.

Plant Material
Lycium minutifolium J. Remy were collected in 2017 at "Cuesta el gato" (Copiapo, III Región, Chile) and identified by Prof. Dra Gloria Rojas from the Museo de Historia Natural, Santiago-Chile. A voucher specimen (Nº LM120217) is kept at the Natural Product Lab. of the Universidad de Chile.

Isolation of Secondary Metabolites
The bark of L. minutifolium was macerated with EtOAc for nine days at room temperature. The crude organic extract obtained after evaporation of the organic solvent was fractionated by flash column chromatography (SiO2) yielding four fractions. Each fraction was subjected to repeated permeation with Sephadex LH-20 and chromatography over silica gel to yield five compounds (1)(2)(3)(4)(5). All compounds were isolated and identified using 1 H-NMR spectroscopic and HR-MS spectrometric techniques and belong to three different classes of compounds: phenylpropanes, flavonoids and coumarins. Among them sarisan 1, methyleugenol 2, eugenol 3, quercetin-3'-methyl ether (isorhamnetin, 4), and scopoletin 5 are reported for the first time in this species ( Figure 2).

Metabolomic Profiling of the Infusion by Using UHPLC-ESI-MS/MS
Ten milligrams of the edible L. minutifolium aqueous extract (EI-EXT) was dissolved in fresh water, filtered and injected in the UHPLC-MS/MS machine ( Figure 3 and Table 1). This infusion was chosen for metabolomic profiling due to the higher biological activity previously shown in comparison to that of ethyl acetate extract (EA-EXT) on the HCl/EtOH-induced gastric lesions model in mice.
Organic acids: Peak 1 with a molecular anion at m/z 191.0557 was identified as quinic acid (C7H11O6 -) [14,15], while peak 2 was identified as citric acid (m/z 191.0199; C6H7O7 -) [16]. Quinic acid is a cyclic polyol common in plants such as coffee, Tara, Eucalyptus, Urtica, and cinchona. Citric acid is common in citrus fruits and is used as flavoring and chelating agent.
Spermine alkaloids: Peak 3 presented a molecular anion at m/z 472.2447 and was identified as N 1 , N 3 -bis-dihydrocaffeoylspermidine (C25H34N3O6 -) and UV absorbance at dihydro caffeoyl structure (287 nm) ( Figure 4). This structure was supported by the presence of two diagnostic fragments at m/z 308.1976 and 163.0393 [17]. Peak 3 was reported as constituent of Scopolia tangutica and Iochroma cyaneum, both belonging to Solanaceae family [18,19]. Peak 6 with a molecular ion at m/z 472.2453 was considered as a potential unknown with MS/MS fragmentation data closely related to a spermidine derivative such as the peak 3 and peak 7 (see Figure S1 in Supplementary Material). This   [5]. Further CC on Fraction 2B (1.1 g) using silica gel afforded compound 5 (scopoletin, 35 mg) [5].

UHPLC-ESI-MS/MS Studies
For this study, an infusion was prepared using 3 g of dried chopped bark parts adding deionized water (200 mL) at 100 • C. Then, the solution was lyophilised (Labconco) to obtain 98 mg of edible aqueous extract (EI-EXT).
A Thermo Scientific Dionex Ultimate 3000 UHPLC system, hyphenated with a Thermo high resolution Q-Exactive focus mass spectrometer (Thermo, Bremen, Germany) was used for the analysis. The chromatographic system was coupled to the MS with a Heated Electrospray Ionization Source II (HESI II). XCalibur 3.0 software (Thermo Fisher Scientific, Bremen, Germany) and Trace Finder 3.2 (Thermo Fisher Scientific, San José, CA, USA) were used for UHPLC control and data processing, respectively. Solvent delivery was performed at 1 mL/min using ultra-pure water supplemented with 1% formic acid (A) and acetonitrile with 1% formic acid (B). A program started with 5% B at zero time, then maintained 5% B for 5 min, then changed to 30% B within 10 min, then maintained 30% B for Foods 2020, 9, 565 5 of 12 15 min, then increased to 70% B for 5 min, then maintained 70% B for 10 min, and finally returned to 5% B in 10 min.

Animals
Mice weighing 30 ± 3 g were acquired from the Public Health Institute, Santiago, Chile. Standard conditions of Swiss albino mice were reported previously [12].

HCl/EtOH-Induced Lesions in Mice
The gastroprotective activity of the Lycium minutifolium extracts was tested at 100 mg/kg on the HCl/EtOH-induced lesion model as described previously [12].

Statistical Analysis
Our results were expressed as the mean ± S.D. Statistical differences between treatments and control were performed by one-way analysis of variance (ANOVA) followed by Dunnett's test. All statistical analyses were performed using the software GraphPad Prism 6 for Windows.

Isolation of Secondary Metabolites
The bark of L. minutifolium was macerated with EtOAc for nine days at room temperature. The crude organic extract obtained after evaporation of the organic solvent was fractionated by flash column chromatography (SiO 2 ) yielding four fractions. Each fraction was subjected to repeated permeation with Sephadex LH-20 and chromatography over silica gel to yield five compounds (1)(2)(3)(4)(5). All compounds were isolated and identified using 1 H-NMR spectroscopic and HR-MS spectrometric techniques and belong to three different classes of compounds: phenylpropanes, flavonoids and coumarins. Among them sarisan 1, methyleugenol 2, eugenol 3, quercetin-3'-methyl ether (isorhamnetin, 4), and scopoletin 5 are reported for the first time in this species ( Figure 2).

Metabolomic Profiling of the Infusion by Using UHPLC-ESI-MS/MS
Ten milligrams of the edible L. minutifolium aqueous extract (EI-EXT) was dissolved in fresh water, filtered and injected in the UHPLC-MS/MS machine ( Figure 3 and Table 1). This infusion was chosen for metabolomic profiling due to the higher biological activity previously shown in comparison to that of ethyl acetate extract (EA-EXT) on the HCl/EtOH-induced gastric lesions model in mice.
Organic acids: Peak 1 with a molecular anion at m/z 191.0557 was identified as quinic acid (C 7 H 11 O 6 − ) [14,15], while peak 2 was identified as citric acid (m/z 191.0199; C 6 H 7 O 7 − ) [16]. Quinic acid is a cyclic polyol common in plants such as coffee, Tara, Eucalyptus, Urtica, and cinchona. Citric acid is common in citrus fruits and is used as flavoring and chelating agent. Spermine alkaloids: Peak 3 presented a molecular anion at m/z 472.2447 and was identified as N 1 , N 3 -bis-dihydrocaffeoylspermidine (C 25 H 34 N 3 O 6 − ) and UV absorbance at dihydro caffeoyl structure (287 nm) ( Figure 4). This structure was supported by the presence of two diagnostic fragments at m/z 308.1976 and 163.0393 [17]. Peak 3 was reported as constituent of Scopolia tangutica and Iochroma cyaneum, both belonging to Solanaceae family [18,19]. Peak 6 with a molecular ion at m/z 472.2453 was considered as a potential unknown with MS/MS fragmentation data closely related to a spermidine derivative such as the peak 3 and peak 7 (see Figure S1 in Supplementary Material). This peak showed two daughter fragments at m/z 308.1975 and 163.0392 considered typical daughter fragments for spermine alkaloids like the peak 3. Peak 6 could be considered a new compound awaiting to be isolated. Peak 7 is a dehydrogenated derivative of peak 3 whose fragments were at m/z 334.1769; 308.1977; 306.1820 and 135.0443. Based on these data peak 7 was identified as N 1 -caffeoyl-N 3 -dihydrocaffeoylspermidine (C 25 H 33 N 3 O 6 − ). Peak 7 has been reported as metabolite in Lycium barbarum [3][4][5]19].
Coumarins: Only esculin was detected in Lycium minutifolium bark based on molecular ion at m/z: 339.0714 and their MS 2 fragment at m/z: 177.0190 (sculetin). This peak 15 has been reported as a constituent of Lycium barbarum [5].
Tropane alkaloids: Peak 9 was tentatively identified as an atropine derivative based on a diagnostic fragment at 149.0601 with a loss of atropine moiety. From Lycium europaeum L. fruits atropine, hyoscyamine and scopolamine have been identified. The presence of these alkaloids could question the safety of Lycium fruit for human consumption [5].
Fatty acids: Peaks 20-22 were tentatively identified as trihydroxyoleic acid and their isomers (C 18 H 33 O 5 ). Remarkably, the presence of oleic acid derivatives was found in Lycium barbarum fruits [5].

Gastroprotective Activity
The effects of the EtOAc extract (EA-EXT) and edible infusion (EI-EXT) in HCl/EtOH induced gastric lesion model in mice are shown in Table 2. The EA-EXT inhibited the gastric lesions by 31% while the EI-EXT by 64% at the dose of 100 mg/kg compared with control group. This dose is valid to show the ethnopharmacological properties of these extracts. In addition, we evaluated the possible mode of gastroprotective action of EI-EXT at a single oral dose of 100 mg/kg. The results of EI-EXT on the gastric lesions induced by HCl/EtOH in mice pretreated with Indometacin (IND, 10 mg/kg, s.c.), N-ethylmaleimide (NEM, 10 mg/kg, s.c.), NG-nitro-L-arginine methyl ester (L-NAME, 70 mg/kg, i.p.), or ruthenium red (RR, 3.5 mg/kg, s.c.) are shown in Table 3. Table 2. Gastroprotective activity of the EA-EXT (organic extract) and EI-EXT (edible extract) on hydrochloric acid (HCl)/EtOH-induced gastric lesions in mice. The results were expressed as mean ± SD * p < 0.01; significantly different compared with the control and ** p < 0.01 significantly different compared with lansoprazole (analysis of variance (ANOVA) followed by Dunnett's test). n = number of mice.
Prostaglandins (PGs) are believed, through PGs production, to be involved in the protection of the stomach mucosa against chemical agents such as ethanol, HCl, and NaOH [21,22]. In our study, pre-treatment with indomethacin (an PGs inhibitor) reduced the gastric protection of EI-EXT (Table 3). This result indicates that PGs are involved in the gastroprotective effect of EI-EXT. Table 3. Protective effect of edible infusion (EI-EXT) on the HCl/EtOH model in indomethacin-, NEM-, L-NAME, and RR-pretreated mice.
The decrease of sulfhydryl (SH) groups have a relationship with gastric lesions induced by ethanol. Glutathione, a known endogenous sulfhydryl, preserves the integrity of the cell and acts as a scavenger of free radicals, an antioxidant, and maintains the immune system as well as protein synthesis and their surface [23]. In our study, pre-treatment with N-ethylmaleimide (NEM, SH-blocker) reduced the protection showed by EI-EXT. This evidence implies that endogenous SHs participate in the gastroprotective activity of this edible extract.
Nitric oxide (NO) is implied in gastric mucosa defense through the regulation of the gastric blood flow, angiogenesis and mucus secretion [24]. In our study, pre-treatment with N G -nitro-L-arginine methyl ester (L-NAME, an inhibitor of NO synthase) reduced the gastroprotective activity of EI-EXT, suggesting that the protective effect of this edible extract is through the participation of endogenous NO (Table 3).
Capsaicin-sensitive sensory neurons through vanilloid receptors on the gastric mucosa protect via the regulation of acid secretion, gastric motility, gastric blood flow and mucus production [1]. In this study, pre-treatment with RR did not produce significant changes in the protection of EI-EXT suggesting that this extract did not imply VR.
Nature has provided many gastroprotective drugs during the last decades including carbenoxolone from Glycyrrhiza glabra, solon from sophoradin and gefarnate from cabbage (Brassica oleracea L.) as the most important gastroprotective agents [23]. So many crude drugs have been reported as gastroprotective agents and this information is summarized in some excellent reviews by Tundis et al., 2008 [25], Mota et al., 2009 [26], Sumbul et al., 2011 [27] and Khan et al., 2018 [28]. Regarding bioactive compounds, a polyssacharide fraction from traditional plant Handroanthus heptaphyllus constituted by arabinogalactans II has showed gastroprotective activity at 10 mg/kg on gastric lesions induced by ethanol. Moreover, this fraction at the same doses presented gastric ulcer healing in rats through the inhibition of mucus and GSH depletion. In another study, a polysaccharide fraction at 100 mg/kg from the medicinal plant Bletilla striata displayed a reduction in the formation of gastric lesions by the increase in PGE2 content, mitigating of oxidative stress, suppression of MAPK/NF-kB signaling pathway in gastric tissue and a reduction in the levels of pro-inflammatory agents as TNF-α, IL-1β, IL-6 and IL-18 [29]. Arunachalam et al., 2019 [30] reported that a hydroethanolic extract of Cochlospermum regium at 100 mg/kg showed preventive and curative activity in different gastric ulcer models supporting the traditional use of this plant. In the same study, it was demonstrated that the mechanism of gastroprotective action and antiulcer activity implied an increase in mucus production, gastric secretion inhibition, activation of K + ATP channels and α-2-adrenergic receptor, augmentation of antioxidant activity and stimulation of PGs and NO synthesis. In the case of Lycium species referred to gastroprotective and ulcerogenic activities, only Lycium chinense has been reported to have these properties [31,32]. An ethyl acetate extract of the aerial part of L. chinense showed gastroprotective activity based on its antioxidant, anti-inflammatory, anti-secretory and anti-apoptotic effects [32]. Pretreatment with ethyl acetate extract at 50-400 mg/kg attenuated the ethanol-induced gastric lesions either increasing oxidative stress markers (GSH and SOD), pH of gastric juice, and mucin soluble content, or decreasing MOP activity, MDA elevation, caspase-3-expresion and inflammatory markers (such as TNF-α, IL-1β, iNOS and COX-2). In a similar way, Cheng et al. 2016 [31] reported gastroprotective properties at doses of 50, 100, 200 and 400 mg/kg of the root bark of L. chinense suggesting that the mechanisms involved could be related to the scavenging of free radicals, antioxidant, anti-inflammatory and pro-inflammatory marker regulations. Lycium barbarum, a closely related plant to Lycium chinense, displayed anti-ulcer activity against water-immersion restraint stress, acetic acid and pylorus-ligation models in rats and this activity was related to the presence of polysaccharides isolated from water extract [33]. In our study, we have demonstrated that edible infusion (100 mg/kg) of L. minutifolium possesses gastroprotective properties against HCl/EtOH induced gastric lesion model in mice suggesting that this protective effect is through the participation of endogenous NO, endogenous SHs, and prostaglandins.
On the other hand, the mortality after peptic ulcer disease decreased significantly in the last few decades, due to treatment of H. pylori infections [34]. Several bioactive compounds were key defensive factors against this bacteria such as: arabinogalactanes (jambo, mangoes, and goji Lycium fruits), other polysaccharides obtained from fruits (Maytenus ilicifolia Mart. ex Reissek) and acidic heteroxylans, (for instance from Olea fruits), rhamnogalacturonanes (ubiquitous in several grapes and ginseng roots) and terpenoids, (such as pinene, lupeol, limonene, citral, nomiline and ursolic acid), and flavonoids such as flavonol derivatives have been showed to display this activity [28,35]. These compounds can prevent the invasion, colonization, and adherence of H. pylori into the cells of the stomach and prevent gastric cancer, suppressing cancer growth, which is very common in H. pylori-infected patients.
The potential bioactivity of this plant could be attributable to the chemical diversity found in the edible infusion such as phenolic acids, alkaloids and flavonoids detected by UHPLC/ESI/MS/MS. These compounds are believed to play an essential role in these bioassays as indicated in our study and others [26,27,36,37]. Further studies are required to isolate and evaluate the gastroprotection of all pure compounds.

Conclusions
In the present study, we isolated five known compounds named as methyl eugenol, sarisan, eugenol, quercetin-3'-methylether (isorhamnetin), and scopoletin for the first time from the ethyl acetate extract of Lycium minutifolium. Then, an edible infusion extract was prepared, and both extracts at 100 mg/kg displayed gastroprotective activity (31% and 64%) on the HCl/EtOH-induced gastric lesion model in mice. Our findings suggest that prostaglandins, sulfhydryl groups, and nitric oxide are involved in the mode of gastroprotective action of this edible extract. Finally, in the edible extract twenty-three compounds were tentatively detected by UHPLC/ESI/MS/MS including diverse compounds such as organic acids, spermine and tropane alkaloids, phenolic acids, flavonoids and fatty acids. Furthermore, peak 6 is considered an unknown spermine-type alkaloid. These results based on ethnomedicinal properties provide the basis for the utilization of L. minutifolium as a source of potential compounds or mixtures for the prevention of gastric ulcers.