Screening of Active Components as Scavenger of Radical from Perennial Fujimoto Bean (Hyacinth Bean) Whole Herb by HPLC MS Coupled Radical Reaction

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1 Original Research Paper Acta Chromatographica 28(2016)1, DOI: / Screening of Active Components as Scavenger of Radical from Perennial Fujimoto Bean (Hyacinth Bean) Whole Herb by HPLC MS Coupled Radical Reaction G.-F. SHI 1, *, Z.-J. WANG 1, G.-Y. WANG 1, **, R.-X. YAO 1, F.-W. CHEN 1, AND Z.-R. SHI 2 1School of Petrochemical Engineering, Lanzhou University of Technology, Lanzhou, Gansu, , China 2College of Life and Environmental Sciences, Shanghai Normal University, Shanghai , China *gaofengshi_lzh@163.com; **gywangcn@126.com Summary. High-performance liquid chromatography mass spectrometry (HPLC MS) method coupled with radical reaction for screening active ingredients from perennial fujimoto bean whole herb was established. The active ingredients, present in perennial fujimoto bean whole herb, possess scavenging effects towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, superoxide, peroxy radical, and hydroxyl radical. The radical scavenging abilities of these active ingredients were evaluated based on the relative peak areas in the HPLC chromatogram. The results indicate that potent antioxidants are present in the anhydrous methanol extract of perennial fujimoto bean whole herb. Based on HPLC MS analysis, it was found that the scavenging ability can be mostly attributed to the presence of three compounds: cyanidin-3-o-β-d-glucopyranoside, troxerutin, and rutin. The structures were identified based on the MS and nuclear magnetic resonance (NMR) data. Free radical scavenging activity decreased in the following order: troxerutin > rutin > cyanidin-3-o-β-d-glucopyranoside. Key Words: perennial fujimoto bean, HPLC MS, antioxidant, radical scavenging capacity Introduction Numerous physiological and biochemical processes in the human body may produce oxygen-centered free radicals and other reactive oxygen species as byproducts. The overproduction of such free radicals can cause oxidative damage to biomolecules (e.g., lipids, proteins, DNA), eventually leading to many chronic diseases, such as atherosclerosis, cancer, diabetes, aging, and other degenerative diseases in humans [1]. Recently, there is a considerable interest in food industry and preventive medicine in the de- First published online: May 14, 2015 ISSN The Author(s)

2 20 G.-F. Shi et al. velopment of natural antioxidants from plant material [2 4]. Plants (fruits, vegetables, medicinal herbs, etc.) may contain a wide variety of free radicals scavenging molecules with anti-oxidization activities, such as flavonoids, anthocyanins, cartenoids, dietary glutathionine, vitamins, endogenous, and metabolites. Among these, flavonoids have been largely studied and proven to possess a multitude of biological properties and to be strong antioxidants and free radical scavengers [5]. The majority oxidant species involved in physiological cellular oxidative events including anion superoxide (O 2 ), hydroxyl radical (HO ), nitric oxide, and peroxyl radical [6, 7]. Thus, searching for new natural antioxidants with antioxidant properties is highly desired. Fig. 1. The photograph of perennial fujimoto bean whole herb (flowers, stems, and leaves) Perennial fujimoto bean (Hyacinth Bean, Lablab purpureus, belongs to Papilionaceae) has attracted enormous attention for its health benefits in the field of medicine in China. Perennial fujimoto bean is a new agriculture vegetable species, which was cultivated through utilizing the infertility of wild lentils as female parent, hybridized with the major oil beans in the northeast of China by a genetic breeding expert Zhou yu-wen, and its patent number is CN The photograph of perennial fujimoto bean whole herb (flowers, stems and leaves) was shown in Fig. 1. This new legume variety is not only a table delicacy but also an oilseed to extract oil. Meanwhile, perennial fujimoto bean can be planted in different environments; it can grow on various marginal lands and bear fruits for many years. After growing for 2 4 years, it will become more productive. Thus, it has been widely used in many features actually. As the Institute of Food Safety

3 Screening of Active Components 21 of Chinese Academy of Inspection Quarantine Comprehensive Test reported, perennial fujimoto bean contains a large amount of full price of protein, eighteen amino acids in its fructification, and plentiful flavones and proanthocyanidins in its flowers, stems, and leaves [8]. To date, although there are many reports on different plants for free radical scavenging, only a few studies about perennial fujimoto bean whole herb as sources of potentially safe natural antioxidants have been reported. The objective of the present study was to evaluate the free radical scavenging activity of the active ingredients extracted from perennial fujimoto bean whole herb by high-performance liquid chromatography mass spectrometry (HPLC MS). The radical scavenging abilities of the active ingredients present in perennial fujimoto bean were evaluated based on the relative peak areas in the HPLC chromatogram, and the structures of the active ingredients were identified through the mass spectrometry (MS) and nuclear magnetic resonance (NMR) analysis. Results from this study may promote the development of plant varieties with enhanced antioxidant properties and demonstrate the potential of developing antioxidant preparations from perennial fujimoto bean whole herb [9 12]. Materials and Instruments Acetonitrile (LC) Methanol, ammonium ferric sulfate, ferrous sulfate, monosodium phosphate, disodium hydrogen phosphate, 1,10-phenanthroline monohydrate, lecithin, ascorbic acid, riboflavin, methionine, ferric chloride, and hydrogen peroxide were of analytical grade (National Institute for the Control of Pharmaceutical and Biological Products, Gansu, China). Free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) was purchased from American sigma-aldrich company. Phosphate Buffer (50/0.75 mm, ph = 7.4) 50/0.75 mm sodium phosphate buffer (ph 7.4) was prepared by mixing 19 ml 50/0.75 mm sodium dihydrogen phosphate with 81 ml 50/0.75 mm sodium hydrogen phosphate.

4 22 G.-F. Shi et al. Instruments LCQ DECA XP Plus Thermo Finnigan, Column, Hypersil GOLD C18 (150 mm 2.1 mm); HP-5988A MS; and Varian INOVA-400 MHz NMR were used. HPLC Mobile phase consisted of acetonitrile and water, which was programmed as follows: CH 3 CN H 2 O, CH 3 CN: 5% 45% 30 min, 45% 80% 45 min, 80% 100% 60 min; flow rate, 0.2 ml min 1 ; detection: PDA and UV detection at 275 nm, spectrum: nm; column temperature, 40 C; injection volume: 5 μl. Mass spectrometric detection was carried out on an ion trap mass spectrometer with an electrospray ionization (ESI), an atmospheric pressure chemical ionization (APCI), and multimode electrospray chemical ionization (ESCI) source. The ESCI multimode ionization spray source was operated in negative mode. The optimal MS parameters were obtained as follows: negative ion mode, capillary voltage, 2.8 kv; corona pin current, 6.3 μa; cone voltage, 60 V; source temperature, 135 C; and desolvation temperature, 350 C. The flow rate of desolvation gas and cone gas were 1000 L h 1 and 50 L h 1, respectively. Argon was used as the collision gas, the pressure of which was approximately 2.8e 3 mbar. Collision energies were 35 V. All data collected in continuum mode were processed using Xcalibur V2.1 software. Experimental Extraction and Separation of Perennial Fujimoto Bean Whole Herb Extracts of perennial fujimoto bean whole herb The whole herb (flowers, stems, and leaves) of perennial fujimoto bean was collected from Gansu province, China in October 2011 and identified by the Chinese Academy of Inspection Quarantine Comprehensive Test. It is deposited at the Plant Photo Bank of China, and the specimen number is LN zbd1DK. The whole herb (flowers, stems, and leaves) of perennial fujimoto bean was dried at 25 C for 13 days before being ground. Then, it was accurately weighed 40.0 g of the powder and extracted with anhy-

5 Screening of Active Components 23 drous methanol. The optimum conditions of microwave extraction are as follows: microwave power, 160 W; the ratio of material to anhydrous methanol, 1:8 (g ml 1 ); and the microwave time, 10 min; extracting times, twice. The supernatant was loaded into a brown bottle after filtering, which was labeled as A and then stored in the refrigerator at 4 C. Isolation and identification of perennial fujimoto bean whole herb Three antioxidant active compounds were purified from perennial fujimoto bean whole herb. About 400 g of perennial fujimoto bean whole herb powder was extracted with anhydrous methanol, according to extraction conditions. All the filtrates were combined and concentrated to dryness under reduced pressure by rotary evaporation at 50 ± 5 C to produce extractum (65.9 g). Then, 60 g of extractum is suspended in water and submitted to liquid liquid fraction using petroleum and ethyl acetate with increasing polarities. This procedure produced ethyl acetate (26 g) and petroleum (9 g). In order to enrich the targeted components, the ethyl acetate was subsequently suspended in water and carried out by silica gel column chromatography (3.0 cm 40 cm), which contained 30 g silica gel ( mesh). Separating target antioxidants by three runs with different solvent systems. At first, chloroform was used to elute the silica gel, then increasing concentrations of ethyl acetate and anhydrous methanol were used to give three main fractions: A, chloroform ethyl acetate anhydrous methanol (5:4:1, v/v/v) was used to isolate rutin (1.43 g); B, chloroform ethyl acetate anhydrous methanol water (1:2:3:5, v/v/v/v) was selected as the optimum solvent system to purify troxerutin (0.79 g); C, ethyl acetate anhydrous methanol (3:1, v/v) was used to isolate cyanidin- 3-o-β-D-glucopyranoside (0.39 g). The structures of rutin, troxerutin, and cyanidin-3-o-β-d-glucopyranoside were identified by MS and NMR, respectively. This is the first report about the separation of antioxidant active compounds from perennial fujimoto bean whole herb by silica gel column. The structures of troxerutin, rutin, and cyanidin-3-o-β-d- glucopyranoside were shown in Fig. 2. Troxerutin: UV (H 2 O, λ max ) 254, 350 nm; MS (ESI+), m/z [M+Na] + at m/z 766.9, 1 H-NMR (400 MHz, DMSO 6 ), δ 0.96 (d, 3H, J = 6.0 Hz, CH 3 ); 7.83 (2 -H); 7.70 (d, 1H, J = 8.8, 6 -H); 7.13 (d, 1H, J = 8.8, 5 -H); 6.74 (d, 1H, J = 1.6, 8-H); 6.38 (d, 1H, J = 1.6, 6-H); (Ph-); 5.43, 5.15, 5.11, 4.51, 4.43 (Glycosyl, ); (CH 2, hydroxy). 13 C-NMR (100 MHz, DMSO6): δ (C=O); (C2); ((C9); (C4); (C4 );

6 24 G.-F. Shi et al (C10); (C3 ); (C7); (C5); (C6); (C5 ); (C6 ); (C3); (C8); (C2 ); (3,4 -OCH 2 ); (7-OCH 2 ); (Glycosyl, CH 2 ); 60.04, 59.99, (HOCH 2 ); ( CH 3 ), 98.86, 93.38, 76.88, 76.45, 74.64, 72.24, 70.86, 70.67, (Glycosyl, CH ). The NMR data are in agreement with those reported earlier [13]. (a) HO HO O HO O O O CH 2 O O (b) (c) Fig. 2. The structure of troxerutin (a), rutinum (b), and cyanidin-3-o-β-d-glucopyranoside (c) The NMR data of fraction A are in agreement with those reported earlier for that rutin isolated from waste tobacco leaves [14]. The NMR data of fraction C are in agreement with those reported earlier for that cyanidin-3-o-β-d-glucopyranoside isolated from fruits of rubus pinnatus and rubus rigidus [15].

7 Screening of Active Components 25 Perennial Fujimoto Bean Whole Herb Free Radical Scavenging Experiment DPPH radical scavenging method DPPH-free radical scavenging capacity of legume extracts was evaluated according to the method by Xu and Chang et al. [16]. Briefly, a dose of 5 ml of A was added to 5 ml ethanol solution of DPPH radical (final concentration was 1.27 mm). The mixture of 5 ml A and 5 ml anhydrous methanol was used as the control solution. The mixture was shaken vigorously and allowed to stand at 37 C in the dark for 1 h. Thereafter, both samples were injected to HPLC MS for analysis after filtered through a 0.45-μm filter. Superoxide radical scavenging method Preparation of superoxide radical. Firstly, g of riboflavin was accurately weighed and dissolved in anhydrous methanol, the volume of which was set with a 10-mL volumetric flask, labeled C. Then, g methionine was accurately fetched and dissolved in anhydrous methanol; the volume of which was set with a 25-mL volumetric flask, labeled as D. Lastly, 5 ml C and 5 ml D were respectively extracted accurately, mixed evenly, loaded into a 10-mL volumetric flask, labeled as E, and stored in the refrigerator at 4 C. Superoxide radical-hplc MS experiment. The experimental sample: 5 ml E and 5 ml A measured accurately were mixed evenly and loaded into a 10-mL volumetric flask. A blank of methanol extraction was used as a control. Control sample: 5 ml A was accurately abstracted and 5 ml of anhydrous methanol was added to it. Both samples were placed under the two UV lamps (365 nm and 254 nm) for 3 h, then passed through a 0.45-μm filter to remove the impurities, and were injected to HPLC MS for analysis. Peroxy radical scavenging method Preparation of peroxy radical g of lecithin was weighed accurately and dissolved in 30 ml of phosphate buffer (50 mm, ph = 7.4), then kept under ultrasonic for 2 h in the ice-water bath, labeled as F, and stored in the refrigerator at 4 C.

8 26 G.-F. Shi et al. Peroxy radical-hplc MS experiment. The experimental sample: extracted 5 ml F and 1 ml of A, and mixed evenly, into which 2 ml of 1 mm ferric chloride and 2 ml of 1 mm ascorbic was then added. Control sample: 1 ml A was added into 2 ml of 1 mm ferric chloride. Afterwards, 2 ml of 1 mm ascorbic and 5 ml of anhydrous methanol were added into the mixture. Both samples were incubated at 37 C for 2 h, impurities were removed by passing through a 0.45-μm filter, and then injected to HPLC MS for analysis. Hydroxyl radical scavenging method Preparation of hydroxyl radical g 1,10-phenanthroline monohydrate was accurately weighed and dissolved in anhydrous methanol; the volume of which was set with a 10-mL volumetric flask, labeled as G, and stored in the refrigerator at 4 C. The experimental sample. 1.5 ml G was accurately extracted. Afterwards, 4 ml of 0.75 mm phosphate buffer (ph = 7.4) was added into it. After being mixed evenly, 1.0 ml of 7.5 nm ferrous sulfate, 2.5 ml of A, and 1.0 ml of 1% H 2 O 2 were added in order. Control sample: 1.5 ml G was extracted, and then 4 ml of 0.75 mm phosphate buffer (ph = 7.4) was added. After being mixed evenly, 1.0 ml of 7.5 nm ferrous sulfate, 2.5 ml of A, and 1.0 ml of anhydrous methanol were added successively. Both samples were incubated at 37 C for 2 h, and then passed through a 0.45-μm filter to remove the impurities, and injected to HPLC MS for analysis. Evaluation of radical scavenging capacity It is a challenging task for the separation of all compounds in complex extract in HPLC for the first time. The peak areas of antioxidants decreased or disappeared in the HPLC chromatogram after spiked with radicals, while for those without antioxidant activities, there was almost no change in their peak areas. The difference of the reduction of peak areas (PA) for radicals between the control sample and the experiment sample was used to evaluate radical scavenging activity of the sample according to the following equation [17 19]: PAcontrol PAexp Radical scavenging (%) = 100% PAcontrol In this equation, PA control is the peak area of the control sample, and PA exp is the peak area of the experimental sample.

9 Screening of Active Components 27 Results and Discussion DPPH Radical Scavenging Activity by HPLC MS At a concentration of 500 ppm solution (perennial fujimoto bean whole herb), the chromatogram of anhydrous methanol fraction of perennial fujimoto bean whole herb spiking with DPPH at 275 nm was shown in Fig. 3. It indicated that the radical scavenging rates of peak 1, peak 2 (compound 1), peak 3, peak 4 (compound 2), and peak 5 were 67.16%, 83.30%, 1.32%, 81.62%, and 2.92%, respectively, which are quite satisfying. Fig. 3. DPPH HPLC of anhydrous methanol fraction of perennial fujimoto bean whole herb These results showed that the radical scavenging activity of the perennial fujimoto bean whole herb methanol extract and its constituents, compound 1 and compound 2, are significant, that is probably because these donate hydrogen atoms for DPPH radical stabilization [20]. Mass spectrometric analyses were performed in the ESI positive ion mode and in the multiple reaction monitoring modes. Only two compounds (1, 2) showed intense molecular ions. Other substances were unstable, so there were no intense molecular ions. The structural identification of compounds (1, 2) related with peak (2, 4) was performed with HPLC MS analysis, and the retained time was the same as that of troxerutin and rutin, respectively, when comparing the above data with the authentic marker and in previous literatures [21]. Results indicate that troxerutin and rutin had strong scavenging effects on DPPH radical.

10 28 G.-F. Shi et al. Superoxide Radical Scavenging Activity by HPLC MS At a concentration of 500 ppm solution (perennial fujimoto bean whole herb), the chromatogram of anhydrous methanol fraction of perennial fujimoto bean whole herb spiking with superoxide radical at 275 nm was shown in Fig. 4. It showed that the radical scavenging rates of peak 1 (compound 3), peak 2 (compound 4), peak 3, peak 4, peak 5 (compound 5), peak 6, peak 7, peak 8, and peak 9 were 1.26%, 37.64%, 10.42%, 35.37%, 10.32%, 1.71%, 38.66%, 0.88%, and 24.39%, respectively. The structural identification of compounds (3, 4, 5) related with peak (1, 2, 5) was performed with HPLC MS analysis, and the retained time was the same as that of cyanidin-3-o-β-d-glucopyranoside, troxerutin, and rutin, respectively; when comparing the above data with the authentic marker and previous literatures [22 25], other substance is unstable, so there is no intense molecular ions. Results indicate that troxerutin and rutin had strong scavenging effects on superoxide radical. Fig. 4. Superoxide radical HPLC of anhydrous methanol fraction of perennial fujimoto bean whole herb Peroxy Radical Scavenging Activity by HPLC MS At a concentration of 500 ppm solution (perennial fujimoto bean whole herb), the chromatogram of anhydrous methanol fraction of perennial fujimoto bean whole herb spiking with peroxy radical at 275 nm was shown in Fig. 5. Results presented that the radical scavenging rates of peak 1 (compo-

11 Screening of Active Components 29 Fig. 5. Peroxy radical HPLC of anhydrous methanol fraction of perennial fujimoto bean whole herb und 6), peak 2 (compound 7), peak 3, peak 4, peak 5 (compound 8), peak 6, peak 7, and peak 8 were 8.68%, 28.61%, 36.77%, 39.22%, 39.76%, 36.89%, 0.15%, and 52.73%, respectively. The structural identification of compounds (6, 7, 8) related with peak (1, 2, 5) was performed with HPLC MS analysis, and the retained time was equivalent to that of cyanidin-3-o-β-d- glucopyranoside, troxerutin, and rutin, respectively. Results indicate that rutin has strong scavenging effects on peroxy radical. Hydroxyl Radical Scavenging Activity by HPLC MS At a concentration of 500 ppm solution (perennial fujimoto bean whole herb), the chromatogram of anhydrous methanol fraction of perennial fujimoto bean whole herb spiked with hydroxyl radical at 275 nm was shown in Fig. 6. It presented that peak area of peak 1, peak 2, peak 3, peak 4, peak 5, and peak 6 decreased after spiking with a hydroxyl radical solution. The radical scavenging rates of peak 1, peak 2 (compound 9), peak 3, peak 4 (compound 10), peak 5, and peak 6 are 81.68%, 74.71%, 96.32%, 43.29%, 0.76%, and 3.68%, respectively. The structural identification of compound (9, 10) related with peak (2, 4) was performed with MS analysis, and the retained time was the same as that of troxerutin and rutin, respectively. It is obvious that troxerutin is qualified as a good scavenger of hydroxyl radical.

12 30 G.-F. Shi et al. Fig. 6. Hydroxyl radical HPLC of anhydrous methanol fraction of perennial fujimoto bean whole herb Conclusions In this study, perennial fujimoto bean whole herb showed highly scavenging ability for DPPH radicals, superoxide anion radicals, peroxy radicals, and hydroxyl radicals, which indicated that rich antioxidants were presented in the anhydrous methanol extract of perennial fujimoto bean whole herb. The scavenging activities against DPPH radicals, superoxide radicals, peroxy radicals, and hydroxyl radicals were most probably due to the presence of three compounds (cyanidin-3-o-β-d-glucopyranoside, troxerutin, and rutin) in the anhydrous methanol extracts of perennial fujimoto bean, which possessed antioxidant activity. The trend of the ranking of antioxidant capacity on the radicals was troxerutin > rutin > cyanidin-3-oβ-d-glucopyranoside. In addition, the troxerutin with an outstanding scavenging ability on the two free radicals was researched. Thus, we make sure perennial fujimoto bean whole herb will be getting more attention for the excellent antioxidant properties because of its active natural compounds.

13 Screening of Active Components 31 Acknowledgments This work was supported by the National Natural Science Foundation of China (No ), Natural Science Foundation of Gansu Province (No. 145RJZA109) and the HongLiu Natural Science Foundation of Lanzhou University of Technology (No. Q201403). References [1] L. Luo et al., Food Chem., 131, (2012) [2] M.A. Esmaeili and A. Sonboli, Food Chem. Toxicol., 48, (2010) [3] C. Sánchez-Moreno, Food Sci. Technol. Int., 8, (2002) [4] R.H. Liu, Am. J. Clin. Nutr., 78, 517S 520S (2003) [5] A. Papadopoulou, et al., J. Agric. Food Chem., 53, (2005) [6] B. Halliwell, Nutr. Rev., 57, (1999) [7] M.E. Letelier, et al., Toxicol. In Vitro, 22, (2008) [8] Z. Hong-yan, et al., Food Sci., 28, (2007) [9] S. Shi, et al., Sep. Purif. Technol., 89, (2012) [10] G.Y. Wang, G. Shi, et al., Anal. Chim. Acta, 802, (2013) [11] G.-Y. Wang, L.-W. Xu, et al., Acta Chromatogr., 23, (2011) [12] G.-Y. Wang, F.-F. Chen, Y.-P. Shi, J. Sep. Sci., 34, (2011) [13] J. Li, B.-M. Xu, K. Liu, Chin. J. Pharm., 35, (2004) [14] F. Fathiazada, et al., Iran. J. Pharm. Res., 5, (2006) [15] B. Robert, T.K. Bernard, et al., J. Food Compos. Anal., 18, (2005) [16] B.J. Xu and S.K.C. Chang, J. Food Sci., 72, (2007) [17] A. Tapia, et al., J. Ethnopharmacol., 95, (2004) [18] Y. Liu, et al., J. Food Sci., 76, C1245-C1249 (2011) [19] L.-Q. Sun, et al., Food Chem., 132, (2012) [20] A.N. Assimopoulou, et al., Phytother. Res., 19, (2005) [21] R.R. Majinda, et al., Planta Med., 63, (2007) [22] Q. Du, et al., J. Food Compos. Anal., 21, (2008) [23] T. Fossen, et al., Food Chem., 63, (1998) [24] T.H. Kang, et al., Neurosci. Lett., 391, (2006) [25] M.-Y. Kim, et al., J. Agric. Food Chem., 51, (2003)