2015 年 21 巻 3 号 p. 333-340
In an effort to identify tea cultivars with high flavonol content, we measured flavonol glycoside levels in the tea infusions of cultivars in the collection of the National Institute of Vegetable and Tea Science. The cultivars ‘Saemidori’, ‘Sofu’, ‘Surugawase’, ‘Fukumidori’, and ‘Asatsuyu’ among others could be effective sources of quercetin compared to other tea cultivars. Quercetin glycosides in “Saemidori” and “Sofu” remained at a relatively high level (110 – 170 µg/mL aglycone equivalent). These cultivars are indicated as effective sources of dietary quercetin, and are potential sources of quercetin-rich drinks.
Some foods contain bioactive components such as polyphenols, which are beneficial to health and reduce the risk of chronic diseases. Quercetin and kaempferol are important bioactive flavonoids, and are most abundantly found in their glycosidic form, i.e., glucoside, galactoside, and rutinoside, in vegetables, fruit, tea, and wine (Tsushida and Suzuki, 1996; McAnlis et al., 1999; Hollman and Katan, 1999; Ono et al., 2010; Calderón-Montaño et al., 2011). Quercetin has been reported to have anti-oxidant (Hur et al., 2011), cholesterol-lowering (Arai et al., 2000), and antidiabetic effects (Azuma et al., 2007). In addition, an 8-year cohort study in Hawaii and California found that intake of flavonols (kaempferol, quercetin, and myricetin) was associated with a reduced incidence of pancreatic cancer (Nöthlings et al., 2007). Onions and green or black tea are important dietary sources of flavonols (Hertog et al., 1992; Hertog et al., 1993). In common onions, the content of quercetin aglycone is 30 – 50 mg/100 g (Hertog et al., 1992), while in tea, the contents of flavonol aglycones (quercetin, kaempferol, and myricetin) are 1 – 2.5, 0.7 – 1.7 and 0.2 – 0.5 mg/100 mL, respectively (Hertog et al., 1993). Although tea is an important source of quercetin, its content is 2% – 5% of that in onions. Recently, an enzymatically modified isoquercitrin (EMIQ)-enriched green tea beverage (145 µg/mL aglycone equivalent) has been introduced to the market, and is reported to have a body fat reducing effect (Akiyama et al., 2000; Egawa et al., 2012). However, flavonol-rich tea cultivars have not as yet been identified. Therefore, in an effort to find tea cultivars with high flavonol content, we determined flavonol glycoside levels in the tea infusions of 45 cultivars in the collection of the National Institute of Vegetable and Tea Science (NIVTS).
Tea Samples Various cultivars of fresh tea leaves (Camellia sinensis L.) were handpicked in April (first crop), June (second crop), and August (third crop) at the NIVTS plantation in Kanaya, Shizuoka, Japan. The freshly picked tea leaves were immediately dried in a microwave oven, finely powdered using a multi-bead shocker (Yasuikikai, Kyoto, Japan) and stored in a refrigerator until analysis.
Chemicals Quercetin-3-O-galactoside (hyperoside), quercetin-3-O-glucoside (isoquercitrin), and quercetin-3-O-rutinoside (rutin) were purchased from Extrasynthese (Genay, France). Myricetin-3-O-glucosyl-(6-O-galloyl)-galactoside, myricetin-3-O-glucosyl-(6-O-galloyl)-glucoside, myricetin-3-O-galactoside, myricetin-3-O-glucoside, quercetin-3-O-glucosyl-(1–3)-rhamnosyl-(1–6)-galactoside, quercetin-3-O-glucosyl-(1–3)-rhamnosyl-(1–6)-glucoside, apigenin-8-C-glucoside (vitexin), kaempferol-3-O-glucosyl-(1–3)-rhamnosyl-(1–6)-galactoside, kaempferol-3-O-glucosyl-(1–3)-rhamnosyl-(1–6)-glucoside, and kaempferol-3-O-rutinoside were kindly provided by Prof. Toshio Miyase (University of Shizuoka). The chemical structures of the compounds used in this study are shown in Fig. 1. Acetonitrile and formic acid were purchased from Wako Pure Chemicals (Osaka, Japan).
Structural formulas of flavonol glycosides analyzed in this study.
Preparation of Tea Infusions Powdered tea was extracted at 4°C for 1 h in a 40-fold dilution with distilled water (w/v). After filtration (2 µm), the flavonol content in the infusion was determined as described in the following section.
LC/MS Analysis Tea infusions were analyzed using a liquid chromatography-mass spectrometer (LC2695, UV2489, MS3100; Waters K.K., Tokyo, Japan). Separations were performed with an Inertsil ODS-3 column (i.d. 4.6 × 250 mm, 4 µm; GL Sciences, Tokyo, Japan). The mobile phase consisted of (A) 0.2% formic acid and acetonitrile at a 85:15 (v/v) ratio, and (B) acetonitrile and (A) at a 40:60 (v/v) ratio. The initial gradient elution consisted of 92% solvent A and 8% solvent B (hold for 5 min), which was increased linearly to 24% solvent A and 76% solvent B over 45 min. In all experiments, the column was kept at 40°C, the flow rate was 1 mL/min, and the injection volume was 10 µL. The UV absorbance detection wavelength was set at 350 nm. Samples were analyzed in positive mode for all experiments. The following MS parameters were used for the analysis in selected ion monitoring (SIM) mode: capillary voltage, 0.6 kV; desolvation temperature, 450°C; source temperature, 150°C; cone gas flow rate, 50 (L/h); desolvation gas flow rate, 900 (L/h).
Flavonol Glycosides in Tea Infusions The structures of flavonol glycosides are shown in Fig. 1. The chromatograms of flavonol glycosides are shown in Fig. 2, and the retention times and mass spectrometric data of 16 compounds in the tea infusions are listed in Table 1. Peaks 1 to 16 in Fig. 2 were determined to be flavonol glycosides. For compound identification, the retention times in the SIM chromatogram of each [M+H]− ion were compared with authentic standards. According to the fragmentation characterization of [M+H]− ions and the retention times, the peaks were identified as myricetin-3-O-glucosyl-(6-O-galloyl)-galactoside (peak 1), myricetin-3-O-glucosyl-(6-O-galloyl)-glucoside (peak 2), myricetin-3-O-galactoside (peak 3), myricetin- 3-O-glucoside (peak 4), quercetin-3-O-glucosyl-(1–3)-rhamnosyl- (1–6)-galactoside (peak 5), quercetin-3-O-glucosyl-(1-3)- rhamnosyl-(1-6)-glucoside (peak 6), quercetin-3-O-rutinoside (rutin; peak 7), kaempferol-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)- galactoside (peak 8), apigenin-8-C-glucoside (vitexin; peak 9), myricetin-3-O-rhamnoside (myricitrin; peak 10), quercetin-3-O-galactoside (hyperoside; peak 11), kaempferol-3-O-glucosyl-(1-3)- rhamnosyl-(1-6)-glucoside (peak 12), quercetin-3-O-glucoside (isoquercitrin; peak 13), kaempferol-3-O-rutinoside (peak 14), kaempferol-3-O-glucoside (astragalin; peak 15), and quercetin-3-O-rhamnoside (quercitrin; peak 16).
HPLC chromatograms of flavonol glycosides in the standard mix solution (A) and ‘Sofu’ green tea infusion (B), and SIM chromatogram of the standard mix and ‘Sofu’ green tea infusion (C). The peak numbers correspond to the peaks listed in the first column of Table 1. The analytical conditions are described in the text. Shaded peaks in graph C are the target peaks.
| Peak No.a | Rt (min) | [M+H]− (m/z) | Cone (V) | Compounds |
|---|---|---|---|---|
| 1 | 7.60 | 633.30 | 25.0 | Myricetin-3-O-glucosyl-(6-O-galloyl)-galactoside |
| 2 | 7.60 | 633.30 | 30.0 | Myricetin-3-O-glucosyl-(6-O-galloyl)-glucoside |
| 3 | 9.37 | 481.20 | 25.0 | Myricetin-3-O-galactoside |
| 4 | 9.79 | 481.20 | 250 | Myricetin-3-O-glucoside |
| 5 | 9.80 | 773.10 | 30.0 | Quercetin-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-galactoside |
| 6 | 10.56 | 773.10 | 30.0 | Quercetin-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-glucoside |
| 7 | 12.66 | 611.40 | 25.0 | Quercetin-3-O-rutinoside (rutin) |
| 8 | 12.69 | 757.40 | 300 | Kaempferol-3-O-glucosyl-(1-3)- rhamnosyl-(1-6)-gaIactoside |
| 9 | 12.93 | 433.20 | 40.0 | Apigenin-8-C-glucoside (vitexin) |
| 10 | 13.54 | 465.01 | 20.0 | Myricetin-3-O-rhamnoside (myricitrin ) |
| 11 | 14.05 | 465.02 | 20.0 | Quercetin-3-O-galactoside (hyperoside) |
| 12 | 14.27 | 757.40 | 30.0 | Kaempferol-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-glucoside |
| 13 | 14.58 | 465.00 | 20.0 | Quercetin-3-O-glucofranoside(isoquercitrin) |
| 14 | 16.77 | 595.07 | 20.0 | Kaempferol-3-O-rutinoside |
| 15 | 18.69 | 449.01 | 20.0 | Kaepferol-3-O-glucoside (astragalin) |
| 16 | 19.23 | 449.02 | 20.0 | Quercetin-3-O-rhamnoside (quercitrin) |
Content of Flavonol Glycosides in Various Tea Cultivars To identify the tea cultivars with high flavonol contents, we measured flavonol glycoside levels in tea infusions from 45 cultivars (Table 2). Peaks no. 1, 2, 9, 10, 15 and 16 were below the lower limit of quantitation (signal-to-noise ratio of S/N=10) in all cultivars; therefore, these peaks were omitted from Table 2. The range of total flavonol glycosides in these infusions was 127.3 – 578.3 µg/mL. The cultivars (2007 season) with the highest total aglycones were ‘Surugawase’, ‘Fukumidori’, ‘Sofu’, and ‘Saemidori’, with contents of 267.2, 225.4, 217.7, and 210.0 µg/mL, respectively. Among the tea cultivars tested, quercetin-3-O-glucosyl-(1-3)- rhamnosyl-(1-6)-glucoside (peak 6) was most abundant in ‘Surugawase’, ‘Saemidori’, ‘Sofu’, ‘Asatsuyu’, ‘Fukumidori’, and ‘Meiryoku’; the content in the infusions was 324.4, 273.0, 261.3, 246.3, 215.2, and 211.1 µg/mL, respectively (Table 2). This quercetin glycoside (peak 6) likely significantly affected the total flavonol content of these tea infusions. Price et al. (1998) reported that the total flavonol glycoside content in black tea infusions (Darjeeling, Ceylon, Keemun, Assam and so on) was 36.5 – 88.3 µg/mL. Thus, the 45 cultivars exhibited relatively high flavonol contents compared with the previously reported teas.
| Peak No. 3 | Peak No. 4 | Peak No. 5 | Peak No. 6 | Peak No. 7 | Peak No. 8 | Peak No. 9 | Peak No. 11 | Peak No. 12 | Peak No. 13 | Peak No. 14 | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cultivar | Myricetin-3-O-galactoside | Myricetin-3-O-glucoside | Quercetin-3-O-glucosy-(1-3)-rhamnosyl-(1-6)-galactoside | Quercetin-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-glucoside | Quercetin-3-O-rutinoside (rutin) | Kaempferol-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-galactoside | Apigenin-8-C-glucoside (vitexin) | Quercetin-3-O-galacloside (hyperoside) | Kaempferol-3-O-glucosly-(1-3)-rhamnosyl-(1-6)-glucoside | Quercetin-3-O-glucoside (isoquercitrin) | Kaempferol-3-O-rutinoside | Total myricetin aglycone | Total quercetin aglycone | Total kaempferol aglycone | Total aglycone | Total glucoside | |
| Green tea cultivars | Fukumidori | 41.2 | 114.5 | 50.4 | 215.2 | 9.2 | 52.1 | 5.5 | 11.3 | 48.1 | 12.7 | 2.3 | 77.8 | 124.1 | 21.5 | 223.4 | 562.5 |
| Minekaori | 48.0 | 56.8 | 89.0 | 84.2 | 5.1 | 119.4 | n.d | 8.0 | 18.0 | 5.1 | 2.1 | 52.4 | 78.7 | 7.9 | 139.1 | 435.8 | |
| Minamikaori | 35.4 | 36.1 | 103.5 | 90.1 | 4.5 | 111.5 | n.d | 6.1 | 15.0 | 3.6 | 1.4 | 35.7 | 84.2 | 6.4 | 126.3 | 407.3 | |
| Izumi | 95.2 | 101.8 | 93.1 | 75.7 | 10.2 | 116.3 | 1.6 | 27.3 | 32.2 | 7.1 | 5.5 | 98.5 | 93.6 | 15.5 | 207.6 | 575.9 | |
| Fushun | 28.7 | 45.3 | 75.8 | 95.6 | n.d | 90.7 | 1.9 | 11.2 | 27.1 | n.d | n.d | 37.0 | 74.2 | 11.0 | 122.3 | 376.3 | |
| Tamamidori | 31.7 | 33.3 | 54.8 | 90.5 | n.d | 72.5 | 1.8 | 7.9 | 19.7 | n.d | n.d | 32.5 | 61.9 | 8.2 | 102.6 | 322.2 | |
| Yamakai | 31.4 | 46.0 | 55.7 | 67.2 | n.d | 67.6 | n.d | 15.0 | 15.1 | 3.0 | n.d | 38.7 | 59.8 | 5.7 | 104.3 | 301.0 | |
| Okumusashi | 32.5 | 23.3 | 1.2 | 169.6 | 4.6 | 17.8 | 1.3 | 31.3 | 21.8 | 3.5 | n.d | 27.9 | 91.9 | 8.8 | 128.6 | 306.9 | |
| Kuritawase | 91.7 | 41.2 | 8.9 | 140.7 | 8.3 | 28.4 | n.d | 38.9 | 19.6 | 6.3 | 1.7 | 66.5 | 92.3 | 8.3 | 167.0 | 385.7 | |
| Shunmei | 35.1 | 25.7 | 62.2 | 72.3 | n.d | 75.9 | 1.5 | 16.1 | 14.7 | 1.9 | 1.6 | 30.4 | 64.4 | 7.0 | 101.7 | 307.1 | |
| Sayamamidori | 45.7 | 26.6 | 10.0 | 87.4 | n.d | 41.9 | 2.2 | 23.3 | 26.5 | 3.8 | n.d | 36.1 | 55.9 | 10.9 | 102.9 | 267.4 | |
| Asagiri | 28.8 | 9.9 | 13.8 | 127.6 | 2.9 | 15.0 | n.d | 27.8 | 7.8 | 7.0 | n.d | 19.4 | 79.6 | 3.0 | 101.9 | 240.8 | |
| Hokumei | 45.9 | 49.1 | 47.4 | 93.7 | n.d | 95.9 | 1.4 | 27.4 | 26.4 | 6.6 | 1.3 | 47.5 | 77.4 | 11.2 | 136.1 | 395.0 | |
| Asahi | 39.8 | 7.1 | 84.7 | 83.3 | n.d | 123.6 | 1.9 | 17.4 | 14.8 | 1.6 | n.d | 23.5 | 78.1 | 6.3 | 107.9 | 374.2 | |
| Sayamakaori | 26.1 | 76.2 | 28.3 | 153.2 | 5.5 | 58.2 | 2.6 | 4.4 | 92.8 | 7.8 | 5.7 | 51.2 | 81.6 | 39.0 | 171.8 | 460.7 | |
| Meiryoku | 45.3 | 66.7 | 43.4 | 211.1 | 3.4 | 66.3 | 5.4 | 4.4 | 82.4 | 3.7 | 3.4 | 56.0 | 106.3 | 35.0 | 197.4 | 535.5 | |
| Kanayamidori | 25.2 | 27.9 | 73.3 | 71.4 | n.d | 90.9 | 2.9 | 4.9 | 13.5 | n.d | 1.4 | 26.6 | 59.6 | 6.9 | 93.1 | 311.4 | |
| Yamatomidori | 34.5 | 14.0 | 6.9 | 87.2 | 5.5 | 24.1 | n.d | 20.0 | 12.3 | 2.9 | 1.3 | 24.3 | 54.5 | 5.3 | 84.1 | 208.7 | |
| Asatsuyu | 36.6 | 55.4 | 41.0 | 246.3 | 15.0 | 31.9 | 2.0 | 11.3 | 48.4 | 6.3 | 3.1 | 46.0 | 131.2 | 20.7 | 197.9 | 497.4 | |
| Toyoka | 40.8 | 38.6 | 51.7 | 110.4 | 5.9 | 82.0 | 3.8 | 11.4 | 30.7 | 3.2 | 1.9 | 39.7 | 75.9 | 14.1 | 129.6 | 380.5 | |
| Yaeho | 27.6 | 37.0 | 21.1 | 87.9 | 12.4 | 34.8 | n.d | 6.5 | 34.6 | 5.9 | 5.0 | 32.3 | 56.9 | 15.6 | 104.8 | 272.8 | |
| Ujihikari | 51.4 | 24.1 | 12.2 | 101.5 | 13.8 | 27.9 | n.d | 29.6 | 13.2 | 7.0 | 2.0 | 37.7 | 75.4 | 6.0 | 119.1 | 282.6 | |
| Ooiwase | 80.5 | 80.6 | 53.9 | 109.1 | 15.8 | 98.0 | 1.7 | 21.6 | 35.7 | 5.9 | 9.9 | 80.5 | 89.6 | 19.1 | 189.2 | 512.7 | |
| Gokou | 42.0 | 28.3 | 104.8 | 71.1 | 4.6 | 114.1 | 1.6 | 14.9 | 9.4 | 4.0 | 1.2 | 35.1 | 83.4 | 4.8 | 123.3 | 396.0 | |
| Inzatsu131 | 51.8 | 95.4 | 24.9 | 166.3 | 11.7 | 26.3 | 1.7 | 11.5 | 31.6 | 4.3 | 3.1 | 73.6 | 90.8 | 14.2 | 178.6 | 428.6 | |
| Surugawase | 43.1 | 102.3 | 7.1 | 324.4 | 24.8 | 9.4 | 2.9 | 14.4 | 84.2 | 9.8 | 6.0 | 72.7 | 157.7 | 36.0 | 266.4 | 628.4 | |
| Samidori | 48.0 | 23.5 | 31.1 | 58.9 | 7.3 | 50.2 | 1.4 | 16.1 | 8.9 | 2.0 | n.d | 35.7 | 50.7 | 3.9 | 90.3 | 247.3 | |
| Ryofu | 36.9 | 68.0 | 32.2 | 156.8 | 6.3 | 98.8 | n.d | 4.7 | 102.8 | 2.7 | 2.6 | 52.4 | 81.7 | 40.4 | 174.5 | 511.9 | |
| Minamisayaka | 25.3 | 15.7 | 26.1 | 45.5 | 1.9 | 62.6 | n.d | 9.9 | 19.9 | n.d | n.d | 20.5 | 35.4 | 7.6 | 63,5 | 206.9 | |
| Saemidori | 26.9 | 111.2 | n.d | 273.0 | 13.4 | 2.0 | n.d | 6.5 | 49.5 | 4.8 | 3.0 | 69.1 | 120.6 | 20.3 | 210.0 | 490.3 | |
| Okuyutaka | 9.9 | 22.0 | 9.3 | 57.2 | 4.8 | 7.0 | n.d | 1.7 | 15.4 | n.d | n.d | 15.9 | 29.4 | 5.8 | 51.2 | 127.3 | |
| Okumidori | 26.8 | 10.4 | 46.8 | 26.3 | 1.4 | 105.8 | n.d | 4.3 | 19.6 | n.d | n.d | 186 | 32.0 | 7.5 | 58.1 | 241.4 | |
| Yutakamidori | 15.5 | 25.0 | n.d | 89.3 | 6.4 | 1.7 | n.d | 4.9 | 29.3 | n.d | 3.2 | 20.3 | 41.2 | 12.7 | 74.2 | 175.3 | |
| Yabukita | 36.5 | 47.7 | 38.7 | 72.6 | 4.5 | 69.8 | n.d | 8.2 | 20.8 | 1.7 | 1.8 | 42.1 | 52.2 | 8.8 | 103.1 | 302.3 | |
| Sakimidori | 34.3 | 16.8 | 31.7 | 53.3 | 4.6 | 56.0 | n.d | 15.7 | 12.6 | 3.4 | n.d | 25.6 | 48.0 | 4.8 | 78.4 | 228.3 | |
| Sofu | 42.9 | 75.6 | 44.7 | 261.3 | 12.2 | 42.9 | n.d | 7.2 | 63.6 | 3.4 | 3.6 | 59.3 | 132.5 | 26.0 | 217.7 | 557.5 | |
| Harumidori | 45.7 | 41.1 | 79.0 | 84.3 | 5.1 | 83.9 | 2.3 | 5.0 | 18.4 | n.d | 1.4 | 43.4 | 69.6 | 8.5 | 121.5 | 366.2 | |
| Oolong tea cultivars | Ohba-oolong | 29.5 | 21.5 | 7.5 | 28.8 | 1.5 | 26.5 | n.d | 12.0 | 13.3 | 2.4 | 1.9 | 25.5 | 24.4 | 6.0 | 55.9 | 144.9 |
| Seishin-taipan | 33.4 | 51.3 | 1.7 | 104.4 | 2.8 | 13.4 | n.d | 7.1 | 45.4 | 6.0 | 2.1 | 42.3 | 51.4 | 18.3 | 122.0 | 267.5 | |
| Seishin-oolong | 50.0 | 111.2 | 3.0 | 95.7 | 4.5 | 4.0 | n.d | 3.5 | 62.6 | 8.0 | 1.8 | 80.6 | 48.3 | 24.7 | 153.5 | 344.1 | |
| Black tea cultivars | Benifuji | 32.5 | 16.9 | 43.5 | 13.3 | 3.3 | 144.5 | 5.4 | 8.5 | 24.8 | 2.1 | 3.2 | 24.7 | 30.8 | 13.0 | 68.5 | 297.8 |
| Benihikari | 19.9 | 92.6 | 1.2 | 140.0 | 11.6 | n.d | n.d | 2.1 | 97.9 | 7.8 | 7.1 | 56.2 | 67.4 | 40.7 | 164.3 | 380.2 | |
| Benihomare | 28.2 | 66.0 | 26.7 | 130.8 | 8.8 | 44.7 | n.d | 6.3 | 90.5 | 9.4 | 6.6 | 47.1 | 76.2 | 37.6 | 160.9 | 418.0 | |
| Hatsumomiji | 13.5 | 85.4 | n.d | 85.0 | 40.4 | 1.6 | 4.7 | 2.1 | 52.8 | 11.9 | 26.7 | 49.4 | 62.6 | 34.9 | 146.9 | 323.9 | |
| Benifuuki | 19.1 | 8.2 | 36.5 | 4.0 | 2.2 | 58.4 | 2.2 | 5.9 | 8.4 | n.d | 1.9 | 13.7 | 20.8 | 5.0 | 39.4 | 146.7 |
* µg/mL, second crop of the 2007 season
* Data are expressed as the mean (n = 3).
* Aglycone content was calculated from the glycoside.
* “n.d” means not detected.
Next, we investigated the flavonol contents under different conditions (year, season, and leaf position) using “Saemidori” and “Sofu”, which are cultivars established by the NIVTS. Table 3 shows the flavonol glycoside contents in tea infusions from different seasons (first crop, April; second crop, June; third crop, August). Kaempferol glycoside contents peaked during the first crop, and myricetin glycosides peaked during the second or third crops (both crops are summer season crops). Quercetin glycoside levels did not show a clear relation to crop season. Table 4 and Fig. 3 show the flavonol glycoside contents in the tea infusions according to leaf age. Most quercetin and myricetin glycosides peaked in the third or fourth leaves, and kaempferol glycosides were mostly contained in younger leaves. In addition, the levels of stem flavonol glycosides were relatively low (Table 4). These results showed the same tendency as a previous report (Forrest and Bendall, 1969). Myricetin and quercetin glycosides were abundant in mature leaves, and kaempferol glycoside levels were high in relatively immature leaves. The synthesis of these flavonol glycosides may be related to the degree of leaf maturity. Catechins (epigallocatechin gallate (EGCG) and epigallocatechin (EGC)) constitute the major flavonoid content of green tea, and are also affected by the crop season and degree of maturity. In a previous study, it was reported that the EGC content in leaves increased as the leaves matured. On the other hand, EGCG content decreased with leaf maturation (Forrest and Bendall, 1969). The flavonol distribution is shown in Fig. 3, and as with EGC, the quercetin content in “Saemidori” and “Sofu” increased with leaf maturation. However, in this study, the EGC content of quercetin-rich cultivars was not notably higher compared with that of other cultivars (data not shown). The synthesis of EGC in tea leaves is strongly affected by sunlight (Saijo, 1980), and EGC synthesis peaked in the second or third crops (summer season crops) (Hilton et al., 1973). The regulation of flavonoid synthesis in tea leaves is affected by phenylalanine ammonia lyase, the activity of which is affected by light intensity (Saijo, 1980). However, in this study, quercetin synthesis was not strongly dependent on crop season, unlike that of EGC (Table 3). Flavonoid synthesis is highly complex, and further studies are needed to fully elucidate the mechanism underlying the synthesis of these flavonoids.
| Peak No. 3 | Peak No. 4 | Peak No. 5 | Peak No. 6 | Peak No. 7 | Peak No. 8 | Peak No. 11 | Peak No. 12 | Peak No. 13 | Peak No. 14 | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| cultivar | Myricetin-3-O-galactoside | Myricetin-3-O-glucoside | Quercetin-3-O-glucosy-(1-3)-rhamnosyl-(1-6)-galaetoside | Quercetin-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-glucoside | Quercetin-3-O-rutinoside (rutin) | Kaempferol-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-galactoside | Quercetin-3-O-galactoside (hyperoside) | Kaempferol-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-glucoside | Quercetin-3-O-glucoside (isoquercitrin) | Kaempferol-3-O-rutinoside | Total myricetin aglycone | Total quercetin aglycone | Total kaempferol aglycone | Total aglycone | Total glycoside |
| First crop | |||||||||||||||
| Saemidori | 22.1 | 16.5 | n.d | 348.9 | 22.1 | 16.5 | 17.7 | 121.4 | 8.3 | 10.2 | 19.3 | 164.3 | 57.4 | 241.0 | 583.6 |
| Sofu | 48.5 | 70.8 | 45.3 | 265.9 | 24.8 | 79.6 | 24.4 | 118.3 | 4.9 | 10.6 | 59.6 | 153.1 | 80.4 | 293.1 | 693.1 |
| Second crop | |||||||||||||||
| Saemidori | 29.6 | 23.9 | n.d | 300.9 | 10.2 | 13.6 | 11.8 | 95.0 | 6.3 | 4.1 | 26.8 | 134.4 | 43.3 | 204.4 | 495.5 |
| Sofu | 81.0 | 131.3 | 57.5 | 331.7 | 17.1 | 61.9 | 15.8 | 87.6 | 6.7 | 5.4 | 106.1 | 175.1 | 59.5 | 340.7 | 795.9 |
| Third crop | |||||||||||||||
| Saemidori | 29.5 | 25 8 | n.d | 299.0 | 12.1 | 7.4 | 11.9 | 38.4 | 5.4 | 3.7 | 27.7 | 134.1 | 19.2 | 181.0 | 433.4 |
| Sofu | 48.8 | 76.2 | 46.7 | 291.5 | 8.8 | 46.8 | 9.0 | 50.7 | 4.9 | 1.6 | 62.5 | 127.2 | 37.9 | 227.6 | 585.1 |
* µg/mL, 2007 season
* Data are expressed as the mean (n = 3).
* Aglycone content was calculated from the glycoside.
* “n.d” means not detected.
| Peak No. 3 | Peak No. 4 | Peak No. 5 | Peak No. 6 | Peak No. 7 | Peak No. 8 | Peak No. 11 | Peak No. 12 | Peak No. 13 | Peak No. 14 | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sofu | Myricetin-3-O-galactoside | Myricetin-3-O-glucoside | Quercetin-3-O-glucosy-(1-3)-rhamnosyl-(1-6)-galactoside | Quercetin-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-glucoside | Quercetin-3-O-rutinosidc (rutin) | Kaempferol-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-galactoside | Quercetin-3-O-galactoside (hyperoside) | Kaempferol-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-glucoside | Quercetin-3-O-glucoside (isoquercitrin) | Kaempferol-3-O-rutinoside | Total myricetin aglycone | Total quercetin aglycone | Total kaempferol aglycone | Total aglycone | Total glycoside |
| Bud + first leaves | 47.0 | 14.0 | 29.2 | 104.1 | 6.7 | 82.7 | 11.4 | 106.5 | 2.6 | 10.5 | 30.5 | 64.5 | 77.0 | 172.1 | 414.5 |
| Second leaves | 73.4 | 34.2 | 67.5 | 251.2 | 13.6 | 95.6 | 24.7 | 162.2 | 8.7 | 21.8 | 53.8 | 153.2 | 108.6 | 315.6 | 753.0 |
| Third leaves | 86.0 | 49.8 | 118.2 | 419.3 | 27.9 | 75.1 | 29.3 | 126.9 | 11.9 | 23.1 | 67.9 | 250.8 | 88.1 | 406.8 | 967.6 |
| Fourth leaves | 73.1 | 51.2 | 108.6 | 428.1 | 30.1 | 59.0 | 22.7 | 95.1 | 9.7 | 20.9 | 62.2 | 245.8 | 68.8 | 376.8 | 898.7 |
| Fifth leaves | 61.4 | 51.0 | 84.3 | 391.7 | 37.0 | 48.5 | 20.2 | 84.1 | 9.3 | 19.7 | 56.2 | 223.6 | 60.0 | 339.9 | 807.2 |
| Stems | 43.4 | 9.9 | 14.4 | 81.7 | 46.8 | 1.7 | 13.1 | 4.9 | 2.6 | 2.3 | 26.6 | 71.3 | 3.6 | 101.6 | 220.8 |
| * µg/mL, first crops of the 2013 season | |||||||||||||||
| Saemidori | |||||||||||||||
| Bud + first leaves | 14.8 | 11.1 | 8.5 | 170.6 | 15.6 | 11.7 | 8.4 | 86.0 | 5.8 | 9.2 | 12.9 | 87.0 | 41.6 | 141.6 | 341.7 |
| Second leaves | 18.1 | 24.0 | 19.9 | 393.6 | 28.5 | 15.7 | 16.1 | 111.2 | 14.2 | 15.3 | 21.0 | 195.5 | 55.7 | 272.3 | 656.5 |
| Third leaves | 18.0 | 26.1 | 17.3 | 380.2 | 29.2 | 13.4 | 14.4 | 89.4 | 11.9 | 13.9 | 22.1 | 187.0 | 45.9 | 255.0 | 613.9 |
| Fourth leaves | 14.0 | 21.8 | 13.7 | 326.0 | 27.6 | 9.8 | 10.8 | 68.6 | 8.3 | 12.4 | 17.9 | 158.9 | 35.8 | 212.6 | 513.0 |
| Fifth leaves | 12.4 | 19.5 | 9.9 | 343.0 | 41.5 | 7.8 | 11.1 | 61.8 | 8.1 | 15.7 | 16.0 | 171.0 | 34.1 | 221.1 | 530.8 |
| Stems | 10.6 | 3.5 | 0.0 | 74.9 | 32.4 | 0.6 | 5.2 | 1.1 | 1.6 | 0.8 | 7.0 | 49.9 | 1.0 | 58.0 | 130.7 |
| * µg/mL, first crops of the 2014 season | |||||||||||||||
| * Data are expressed as the mean (n = 3). | |||||||||||||||
| * Aglycone content was calculated from the glycoside. | |||||||||||||||
The concentrations of flavonol aglycone in ‘Sofu’ and ‘Saemidori’ green tea infusions. A, ‘Sofu’ green tea infusion. B, ‘Saemidori’ green tea infusion. Powdered tea was extracted by 40-fold dilution in distilled water (w/v). This figure was generated from Table 4.
Table 5 shows the yearly fluctuation in flavonol content in “Saemidori” and “Sofu”. Quercetin aglycone, which represents the greatest contribution to total flavonol content, fluctuated in the range of 110 – 170 µg/mL, and its content remained at a relatively high level. Meanwhile, a quercetin glucoside-enriched green tea beverage contains 110 mg of EMIQ per 500-mL bottle (145 µg/mL quercetin aglycone equivalent), and is reported to exert a body fat reducing effect (Egawa et al., 2012).
| Saemidori | Myricetin-3-O-galactoside | Myricetin-3-O-glucoside | Quercetin-3-O-glucosy-(1-3)-rhamnosyl-(1-6)-galactoside | Quercetin-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-glucoside | Quercetin-3-O-rutinoside (rutin) | Kaempferol-3-O-glucosyl-(1-3)-rhamnosyl-(1-6)-galactoside | Quercetin-3-O-galactoside (hyperoside) | Kaempferol-3-O-glucosyl-(1-3)-rhamnosyl-(1-6) glucoside | Quercetin-3-O-glucoside (isoquercitrin) | Kaempferol-3-O-rutinoside | Total myricetin aglycone | Total quercetin aglycone | Total kaempferol aglycone | Total aglycone | Total glycoside |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2003 | 19.6 | 72.0 | n.d | 354.5 | 33.1 | 6.7 | 10.0 | 79.7 | 8.8 | 12.0 | 45.8 | 167.2 | 38.7 | 251.7 | 596.4 |
| 2006 | 18.2 | 37.5 | n.d | 313.5 | 31.5 | 11.5 | 10.2 | 98.6 | 7.6 | 9.9 | 27.8 | 149.7 | 46.7 | 224.3 | 538.4 |
| 2007 | 26.9 | 111.2 | n.d | 273.0 | 13.4 | 2.0 | 6.5 | 49.5 | 4.8 | 3.0 | 69.1 | 120.6 | 21.0 | 210.7 | 490.3 |
| 2009 | 19.7 | 40.3 | n.d | 256.5 | 16.8 | 12.3 | 9.5 | 95.9 | 5.7 | 6.2 | 30.0 | 118.4 | 44.1 | 192.6 | 462.8 |
| 2010 | 18.3 | 41.4 | n.d | 249.6 | 15.3 | 16.1 | 8.5 | 101.7 | 5.1 | 6.4 | 29.8 | 114.0 | 47.9 | 191.7 | 462.3 |
| 2011 | 21.6 | 44.1 | 1.3 | 308.7 | 27.1 | 15.3 | 11.4 | 105.5 | 7.6 | 9.6 | 32.9 | 147.0 | 50.6 | 230.5 | 552.2 |
| 2012 | 17.2 | 33.5 | n.d | 240.4 | 14.7 | 14.3 | 8.3 | 102.5 | 4.9 | 6.2 | 25.3 | 109.8 | 47.4 | 182.6 | 442.0 |
| 2013 | 23.7 | 50.0 | 1.5 | 352.0 | 36.1 | 16.0 | 12.7 | 105.8 | 9.0 | 10.4 | 36.8 | 170.3 | 51.4 | 258.4 | 617.1 |
| 2014 | 16.7 | 13.4 | 12.3 | 222.1 | 21.9 | 13.9 | 10.5 | 76.8 | 6.2 | 7.4 | 15.1 | 113.4 | 38.1 | 166.6 | 401.3 |
| Sofu | |||||||||||||||
| 2007 | 42.9 | 75.6 | 44.7 | 261.3 | 12.2 | 42.9 | 7.2 | 63.6 | 3.4 | 3.6 | 59.3 | 132.4 | 42.2 | 233.9 | 557.4 |
| 2012 | 42.6 | 78.7 | 51.0 | 292.1 | 32.5 | 70.5 | 15.1 | 109.8 | 4.6 | 11.1 | 60.6 | 163.1 | 73.9 | 297.6 | 707.9 |
| 2013 | 38.5 | 49.3 | 27.5 | 218.8 | 38.9 | 41.0 | 13.9 | 65.2 | 2.5 | 6.3 | 43.9 | 126.3 | 43.4 | 213.6 | 501.8 |
| 2014 | 25.1 | 14.0 | 70.1 | 208.4 | 10.4 | 54.9 | 7.4 | 85.5 | 2.5 | 6.0 | 19.5 | 120.4 | 56.3 | 196.2 | 484.3 |
* µg/mL, first crop
* Data are expressed as the mean (n = 3).
* Aglycone content was calculated from the glycoside.
* “n.d” means not detected.
Tea is an important dietary source of flavonols, and tea cultivars such as ‘Saemidori’, ‘Sofu’, ‘Surugawase’, ‘Fukumidori’, and ‘Asatsuyu’, among others, could be effective novel sources of quercetin, and represent potential sources of quercetin-rich drinks.
