Antihyperlipidemic and Antioxidant Capacities, Nutritional Analysis and UHPLC-PDA-MS Characterization of Cocona Fruits (Solanum sessiliflorum Dunal) from the Peruvian Amazon

Cocona fruits are a popular food and medicinal fruit used mainly in the Amazon and several countries of South America for the preparation of several food products such as drinks, jams and milk shakes. In this study five ecotypes of cocona native to Peru have been studied regarding their nutritional and antioxidants values plus antihyperlipidemic activities. Seventy bioactive compounds have been detected in Peruvian cocona ecotypes including several phenolic acids, aminoacids and flavonoids; of those six were spermidines, (peaks 1, 2, 25, 26, 38 and 39), thirteen were aminoacids, (peaks 3–9, 11–13, 16, 17, 22–24), eighteen flavonoids (peaks 28, 30–32 45,46, 48–53 56, 57, 61 and 64–66), twelve were phenolics (peaks 19, 21, 27, 29, 34, 35, 36, 42, 43, 44, 54, and 59), two carotenoids, (peak 62 and 63), eight were lipid derivatives (peaks 37, 55, 58, 60 and 67–70), one sugar (peak 47), four terpenes (peaks 33, 40, 41 and 47), two amides, (peaks 10 and 18), one aldehyde, (peak 15), and three saturated organic acids, (peaks 4, 5 and 20). Hypercholesterolemic rats administered with pulp of the ecotypes CTR and SRN9 showed the lowest cholesterol and triglyceride levels after treatment (126.74 ± 6.63; 102.11 ± 9.47; 58.16 ± 6.64; 61.05 ± 4.00 mg/dL, for cholesterol, triglycerides, high-density lipoprotein and low-density lipoprotein respectively, for the group treated with SRN9 pulp, and 130.09 ± 8.55; 108.51 ± 10.04; 57.30 ± 5.72; and 65.41 ± 7.68 mg/dL, for cholesterol, triglycerides, HDL and LDL lipoproteins respectively for the group treated with CTR pulp). The ecotypes proved to be good sources of natural antioxidants and their consumption represent an alternative for the prevention of atherosclerosis.


Introduction
In recent decades, global interest has increased in search of the chemical composition and biological activities of natural sources since many of the compounds present in biological sources such as local plants and marine organisms are important for the protection of human health. The fruit of cocona (Solanum sessiliflorum Dunal; Solanaceae) are native of the Amazonian tropic. Just like other plants in the genus Solanum, they exhibit a morphological diversity corresponding to the variability in habitat and ecology changes, as well as with the process of domestication of the species; However, little is known about its chemical composition and the implications of the terroir and climate in its morphology and nutrient and health beneficial properties. The common name of the fruit in Spanish or Portuguese speaking countries is cocona, topiro or cubiu, and is known as "Orinoco apple" and "peach tomato" in English speaking countries. It is an endemic species to Amazon cultivated by natives and settlers in agroforestry arrangements and chagras in their settlement sites which improves it on a traditional food from this area. The pulp is the edible part of the fruit and is known for its refreshing flavor to produce refreshments, milk shakes, jams, and jellies and for the medicinal properties, including amelioration of itching produced by insect bites, elimination of parasites, it is also use as topical to heal burns and for the control of cholesterol, diabetes, and uric acid. The studies carried out on the chemistry of the species are few and no complete, mainly limited to the report of some phenolic compounds and volatile metabolites which cannot depict the differentiation in the variations in the chemical composition between the different morphotypes of the fruit which is very important to give added values to the different products and ecotypes. This study aimed to differentiate five varieties of cocona ( Figure 1) with the use of UHPLC coupled to high resolution mass spectrometry (UHPLC-PDA-ESI-OT-MS) grown in Peru, called oval, small round, large round big oval round and big square morphotypes, by means of the metabolite fingerprinting of the secondary metabolites present in mature fruits of the species. These adaptive morphotypes of the fruit depends directly on various biological factors and has been diversifying during the evolution and natural selection and can have the ability to produce different biologically important metabolites. Several carotenoids, alkaloids, organic acids, phenolic acids, flavonoid glycosides, coumarins, tannins, and volatile and fixed acids were reported to occur in fresh cocona fruits from Brazil [1,2] and recently, caffeoyl quinic acid was reported as the main important phenolic in the fruits [3], whereas determination of volatile organic compounds (VOCs) was done by HS-SPME/GC-MS in some ecotypes from Brazil [4], besides, extracts of those Brazilian ecotypes presented high concentrations of caffeic and gallic acids, betacarotene, catechin, quercetin, and rutin and showed low density lipoproteins oxidation; cytotoxic and antiproliferative effect on breast (MCF-7) and colorectal (HT-29) cancer cell lines [5]. The purpose of this work is to contribute to the full phytochemical study of the Peruvian ecotype species through UHPLC-PDA-ESI-OT-MS for full untargeted metabolomic analyses to promote in fruit growers and fruit processors in the Peruvian Amazon the adoption of strategies for the sustainable use of the more promising ones based on its phenolic content and intrinsic health related properties, such as antihyperlipidemic capacities of the studied five ecotypes of this highly consumed fruit from Peru. Finally, proximal composition and mineral contents, plus the antioxidant activities thorough different methods and total carotene and phenolic contents of all ecotype pulps were tested and compared. The UHPLC full MS and PDA fingerprint analysis, was also performed for the ecotypes.

Plant Material and Sample Treatment
The study was carried out with five ecotypes of Solanum sessiliflorum, whose seeds were obtained from the ex situ conservation gene bank of the Peruvian Amazon Research Institute, cultivated in the Research and Production Center of Tulumayo of the National Agrarian University of the Jungle (09 • 06 20 S and 75 • 54 15 W, 565 meters altitude) Huanuco region, Peru. The ecotypes were selected based on their morphotypic difference, which were: CTR, collected in cascas, Lambayeque region, SRN9, collected in Supte Black river, Huanuco region, UNT2, collected in Padre Abad, Ucayali region, NMA1, collected in Leoncio Prado, Huanuco region, and CD1, collected in Bagua, Amazonas region. The selected fruits were washed, brushed, disinfected using a 200-ppm sodium hypochlorite solution for 30 min and rinsed with water. The epicarp was then removed. Then thermal bleaching was carried out at 90 • C for 20 min. The pulp was then extracted in a pulping machine removing the husks and seeds. Finally, the extracted pulp was lyophilized. The lyophilized pulp was packed in plastic bags and stored in a freezer at −20 • C until use (for some days only). Lyophilized pulp (2.0 g) was extracted two times in 5 mL of methanol/water (MeOH/H 2 O) solutions (80/20, v/v) under sonication (130 kHz, 10 min) at room temperature. Then, samples were centrifuged (5000 rpm, 15 min, 5 • C) and the supernatants were combined after filtration and stored at −20 • C before analyses.

UHPLC-PDA-ESI-OT-MS Instrument
UHPLC-PDA-ESI-OT-MS analysis was carried out as described by [6], with some modifications, Briefly, a Thermo Scientific Dionex Ultimate 3000 UHPLC system hyphenated with a Thermo Q exactive plus machine was used. For the analysis 5 mg of the extract were dissolved in 2 mL of methanol, filtered (PTFE filter) and 10 µL were injected in the instrument, using an UHPLC C-18 column (Luna© Omega C-18 100 Å, Phenomenex 150 mm × 2.1 mm × 1.6 µm), operated at 25 • C. The detection wavelengths were 254, 280, 330 and 354 nm, and PDA was recorded from 200 to 800 nm for peak characterization. Mobile phases were 1% formic aqueous solution (A) and 1% formic acid in acetonitrile (B). The gradient program (time (min), % B) was: (0.00 min, 5% B); (1.500 min, 15% B); (1.5 min, 5% B); (35.00 min, 95% B); (36.00, 95% B); (38.00 min, 5% B); and 15 min for column equilibration before each injection. The flow rate was 0.300 mL min −1 , and the injection volume was 10 µL. Standards and the pulp extract dissolved in methanol were kept at 10 The DPPH• radical was assayed by the decolorization method [7]. Briefly, 9 µL of extract, (2 mg/mL), plus 341 µL of methanol DPPH solution (400 µM) were adjusted with the solvent methanol to an absorbance of 1.10 ± 0.02 at 517 nm. The mixture was homogenized using a vortex, allowed to react in the dark at room temperature for 20 min, after which time absorbance was measured at 517 nm in a Synergy HTX monochromator (Biotek, USA). The percentage of decoloration of the DPPH moiety was obtained by measuring the change in absorbance at 517 nm, the values obtained converted to percent inhibition of the DPPH moiety. The results are expressed in TEAC, that is, antioxidant activity equivalent to Trolox (µmol Trolox/g of lyophilized pulp). The synthetic antioxidant reference Trolox, at a concentration of 5-30 µM in 80% methanol solution, is tested under the same conditions.

ABTS Method
The ABTS assay was performed by bleaching of the cationic radical ABTS •+ as described by [8]. For the preparation of the radical ABTS •+ 2.5 mL of the 7 mM ABTS solution, it was mixed with 2.5 mL of 2.45 µM sodium persulfate for 12 hours in the dark at 4 • C. Then, the resulting solution was diluted with absolute ethanol until an initial absorbance of approximately 0.70 ± 0.03 was obtained at 734 nm. The radical discoloration was initiated by adding 50 µL of the extract to 150 µL of the ABTS •+ solution. After 15 minutes of incubation at 25 • C, the absorbance was measured at 734 nm and compared with a calibration curve using Trolox as standard and ethanol as blank. Results were expressed as micromoles of Trolox equivalents per gram of dry sample (µmol TE/g).

Polyphenol (Folin-Ciocalteau)
Total phenolic compounds (TPC) were analyzed based on [6] and [9]. To 12 µL of extract to be measured, 168 µL of the 1% Folin-Ciocalteu reagent (Merck, Santiago, Chile) were added to well of a microplate reader. The mixture could react for 5 min, then 120 µL of 10% sodium carbonate was added. The mixture was incubated at room temperature for 30 min in darkness. Absorbance was then taken at 765 nm using an UV-Visible multiplate reader (Synergy HTX, Biotek, Winooski, VT, USA). The obtained absorbance values were replaced in the equation of the standard curve of gallic acid (µmol/L). The content regarding phenolic compounds was then expressed as gallic acid milligrams per gram of dry weight (mg GAE/g extract).

Determination of Proximal Composition
Water content was determined by oven drying the sample up to a constant weight, the crude protein content by the Kjeldahl method (N × 6.25), the fiber content by gravimetric method after acidic hydrolysis of the samples, the total lipid extracted in a Soxhlet apparatus using petroleum ether as solvent, the ash content by incineration in a muffle furnace at 550 ± 15 • C. AOAC procedures were used in all determinations [10].
Total carbohydrates were calculated as difference: 100 − (g water + g protein + g fiber + g fat + g ash). Results were expressed in g per 100 g fresh weight (g/100 g fw).

Mineral Analysis
For the mineral analysis [11], the fresh fruits pulps were dry ashed at 550 • C. The ash in each case was boiled with 10 ml of 20% hydrochloric acid in a beaker, and then filtered into a 100 mL standard flask and made up to 100 ml with distilled deionized water. Levels of minerals, sodium (Na), potassium (K), magnesium (Mg), manganese (Mn), copper (Cu), zinc (Zn), iron (Fe) and calcium (Ca) were determined from the resulting solution using atomic absorption spectroscopy (Varian AA240). The values obtained for each parameter are averages of three determinations for a given food sample.

Total Carotene Content
Total carotenoids were extracted with hexane, acetone and ethanol. The supernatant from the hexane phase was extracted, rich in carotenoids, and its absorbance at 450 nm was determined. The calculation of total carotenoids was performed by comparison with a calibration curve obtained with a certified β-carotene standard [12]. The results were expressed as µg β-carotene g −1 sample.

Induction of Hypercholesterolemia
For experimental induction of hypercholesterolemia, male albino rats of the Wistar strain (150-200 g) were housed under conditions of controlled temperature (25 ± 2 • C) with a 12 h/12 h day-night cycle, during which time they had free access to food and water ad libitum. Animals were maintained per national guidelines and protocols of guide for the handling and care of laboratory of the National Institute of health. Hypercholesterolemia was induced experimentally in 12 h-fasted rats by a single intraperitoneal injection of Triton WR-1339 (300 mg/kg Body weight (b.wt.)) dissolved in 0.89% saline [13]. Forty-eight hours after administration of Triton WR-1339, rats exhibited elevated serum levels of total cholesterol and triglycerides; these rats were deemed to be hypercholesterolemic and use for further investigation. The experimental rats were divided into eight treatment groups, each comprising six rats. Group I. Control rats (not hypercholesterolemic and did not receive any treatment). Group II. Hypercholesterolemic rats that received only saline orally for three days. Group III. Hypercholesterolemic rats that received atorvastatin (10 mg/kg b.wt./day) in an aqueous suspension orally for three days. Group IV. Hypercholesterolemic rats that received the NMA1 lyophilized pulp ecotype (500 mg/b.wt./day) in an aqueous suspension orally for 3 days. Group V. Hypercholesterolemic rats that received the CD1 lyophilized pulp ecotype (500 mg/b.wt./day) in an aqueous suspension orally for 3 days.
Group VI. Hypercholesterolemic rats that received the CTR lyophilized pulp ecotype (500 mg/b.wt./day) in an aqueous suspension orally for 3 days. Group VII. Hypercholesterolemic rats that received the SRN9 lyophilized pulp ecotype (500 mg/b.wt./day) in an aqueous suspension orally for 3 days. Group VIII. Hypercholesterolemic rats that received the UNT2 lyophilized pulp ecotype (500 mg/b.wt./day) in an aqueous suspension orally for 3 days. Saline, atorvastatin and NMA1, CD1, CTR, SRN9, UNT2 lyophilized pulp ecotypes were administered orally by gastric intubation once daily for 3 days. Blood samples were collected from all experimental rats on day 6 (3 days after start of treatment), and, subsequently, serum was separated for subsequent analysis of serum lipid profile parameters. Mean levels of total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol and low-density lipoprotein (LDL) cholesterol were determined by standard kits (Stambio, Boerne, TX, USA) following the manufacturer's instructions. The units being expressed as milligrams per deciliter (mg/dL).

Statistical Analysis
The statistical analysis was carried out using the originPro 9.1 software packages (Originlab Corporation, Northampton, MA, USA). The determination was repeated at least three times for each sample solution. The Tukey comparison test determined significant differences between means (p values ≤ 0.05 were regarded as significant). Table 1 shows proximal composition such as the humidity, ashes, protein, lipids, carbohydrates, and fiber, while Table 2 shows the mineral contents of five ecotypes of cocona. Proximal composition of cocona fruits NMA1, SRN9, CD1, CTR, UNT2 ecotypes was performed. The results of physicochemical properties showed that the proximal composition and the caloric value of this fruit are similar to that showed for other species, but with a high fiber (from 1.08 to 1.93) and carbohydrate content (from 3.12-4.24). The edible portion of cocona ecotypes were analyzed for mineral content (Ca, Na, Mg, K, Cu, Mn, Zn, and Fe). The foods were generally high in K (570.83-2382.24 mg K/100 g edible portion) and low in sodium (3.25-6.87 mg Na/100 g edible portion). The five ecotypes had the highest contents in most of the elements, especially in calcium (17.85-70.07 mg Ca/100 g edible portion) and iron (52-71 mg Fe/100 g edible portion).

Metabolite Profiling using UHPLC-PDA-ESI-OT-MS
The metabolite profiling was comprehensively performed by UHPLC-PDA-ESI-OT-MS, while Figure 2 shows the base peak UHPLC-mass chromatograms of ecotypes of cocona fruits and Table 3 shows the tentative identification of metabolites detected in the five ecotypes. Below are the detailed analyses, while Figure 3 show the structures of some representative compounds.

Amines or Aminoacids
Several aminoacids were previously reported using orbitrap mass spectrometry by some of us [17]. Peak 3 was identified as histamine (C 5 H 9 N 3 ), peak 6 as asparagine (C 4

Phenolic Acids
Peak 19 was tentatively identified as chlorogenic acid (C 8  Several acyl quinic acids such as ferulic, sinapic and chlorogenic acid and derivatives showed different interesting bioactivities such as anti-inflammatory, vasorelaxant in mice aorta, platelet activation in human blood samples neuroprotective effects among others [24], while the glycoside derivative of the lignan syringaresinol enhanced ß-endorphin levels in rat plasma, [25] while syringaresinol aglycone was cytotoxic against human breast and lung cancer cells [26].

Citric Acid
Peaks 5 and 6 were assigned as citric acid and isocitric acid (C 6 H 8 O 7 ) respectively.

Carotenoids
Peaks 62 and 63 were tentatively identified as lutein (C 40 H 56 O 2 ) and β-carotene (C 40 H 56 ), respectively. In this study other carotene compounds were not detected, probably due to destruction by the pulping procedure. Lutein showed antioxidant and antiinflammatory capacities, [39], and carotene showed anti-inflammatory, antioxidant and anticancer activity [40] and their presence in cocona fruits is in concordance with the medicinal.

Antioxidant Activity, Total Carotenes and Total Polyphenols Content
In this study the antioxidant capacities of the five ecotypes were assessed by the trapping of ABTS and DPPH and expressed as µmol Trolox/g dry matter (Table 4). In addition, total phenolic contents by the Folin and Ciocalteau's method plus the total carotenes was assessed and correlated with the antioxidant capacities. Trapping of ABTS and DPPH radicals showed similar values in the different ecotypes and correlated with carotene and phenolic contents for the dry pulps. Strong correlation was found between total phenolics and DPPH antioxidant assays (r = 0.847, p < 0.0001). Moderated correlation was found between total carotenoids and ABTS antioxidant assays used (r = 0.640, p < 0.011). Ecotype UNT2 showed the highest DPPH• radical scavenging capacity in terms of content of Trolox equivalents (23.29 ± 1.07 µmol Trolox/g), but interestingly, in ABTS• radical scavenging activity the most powerful was the CD1 ecotype (25.67 ± 0.28 µmol Trolox/g).  Table 5 shows the variations in cholesterol, triglycerides, HDL and LDL in the different study groups. The highest cholesterol and triglyceride values correspond to the hypercholesteremic group that only received saline treatment (group II), with a statistically significant difference (p < 0.05) with the group control (group I) for the variables considered, thus corroborating the effectiveness of the model used. The increases obtained with Triton were 370 and 600 % for cholesterol and triglycerides, respectively. Several authors report similar elevations in the lipid profile of rodents treated with this agent. For instance, Harnafi et al. [41], obtained elevations of 270% for cholesterol and up to more than 1000% for triglycerides; while Khanna et al. [42], reported an elevation of cholesterol by 134%, these differences seem to depend on the strain of animals used. When comparing the groups treated with the pulps, we noticed that samples which has received the CTR and SRN9 pulps showed the lowest cholesterol and triglyceride levels after treatment, however there is no clear correlations with the compounds detected and bioactivity showed by pulps. In agreement to the above, there isn't a statistically significant difference (p < 0.05) between the cholesterol and triglyceride levels of the hypercholesterolemic group that received treatment with atorvastatin and the groups that received treatment with CTR and SRN9 pulps; which suggests that the treatment of the experimental animals with two pulps brings cholesterol levels closer to their basal values; this result is very important since it is an indicator of the effectiveness of the pulps tested. Regarding carotene compounds present in cocona fruits, it has been proved that diet with carotenes at a dose 80 mg/kg in rats decreased the lipid serum concentrations and its effect was comparable to that of simvastatin [43]. Regarding anthocyanins, also detected in cocona fruits, a juice from the fruit Aronia containing 106.8 mg cyanidin-3-glucoside equivalents/100 mL juice and 709.3 mg gallic acid equivalents/100 mL juice, showed an antihyperlipidemic effect in rats with hyperlipidemia and was proved to be valuable in re-ducing factors of cardiovascular risks [44]. Moreover, mulberry (Morus alba L.) lyophilized fruit administered to rats proved to have significant decrease in levels of serum and liver triglycerides, total cholesterol, serum low-density lipoprotein cholesterol, and a decrease in the atherogenic index, while the serum high-density lipoprotein cholesterol was significantly increased [45]. Several flavonoids and extracts rich in flavonoids were attributed anti hyperlipidemia activities; Pterocarpus marsupium heartwood and its flavonoid constituents, marsupsin, pterosupin, and liquiritigenin were able to effect a significant fall in serum cholesterol, LDL-cholesterol, and atherogenic index [46], also extracts full of glycosylated flavonoids from Cardoncellus marioticus showed antioxidant and antihyperlipidemic activities [47] moreover, using our same triton induced hyperlipidemia system extracts from the Mediterranean buckthorn, Rhamnus alaternus full of flavonoids decreased blood levels of cholesterol and triacylglycerols in hyperlipidemic rats (by 60% and 70%, respectively, at 200 mg CME/kg) [48]. In this study, all groups treated with the pulps showed a significant reduction in LDL-C (p < 0.05) with respect to the negative control group (group II), with the SRN9 group showing the best results. Despite the reduction in total cholesterol obtained with the different pulp treatments, we can observe that none of the treatments achieved lower values than the group treated with atorvastatin. In all the groups evaluated, an increase in HDL-C concentration was observed, the increase being significant in the groups that received CTR and SRN9 pulp (p < 0.05); the best result obtained was in the group that received SRN9 pulp after 96 hours of treatment. From the above mentioned we can say that SRN9 pulp, presents the best result of inhibition of the surfactant used (Triton WR-1339), by significantly decreasing the serum concentrations of cholesterol and triglycerides, corroborating the traditional use of this species and previous reports on its antihyperlipidemic activity [49,50]. This allows us to affirm that SRN9 pulp at the doses tested shows an antihyperlipidemic effect and could be an option in the management of people with high lipid levels. The presence of phenolic compounds, including flavonoids, could explain the hypolipidemic effect shown, presumably due to their proven antioxidant activity, as a result of a combination of their iron chelating and free radical scavenging properties [51,52]. During the experimental phase, no toxic effects were evidenced in the experimental specimens treated with NMA1; CD1; CTR; SRN9 and UNT2 pulps.