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Dihydroquercetin as an Antioxidant
二氢槲皮素作为抗氧化剂

E. F. KURTH 1 1 ^(1){ }^{1} and FRANK L. CHAN 2 2 ^(2){ }^{2}
E. F. KURTH 1 1 ^(1){ }^{1} 和 FRANK L. CHAN 2 2 ^(2){ }^{2}

DIHYDROQUERCETIN has been found in Douglas fir heartwood (4), and as much as 20 % 20 % 20%20 \% of this material has been obtained from the cork portion of Douglas fir bark, Pseudotsuga taxifolia (Poir.) Britt. (7). It also has been isolated in this laboratory from the bark of Jeffrey pine, Pinus jeffreyi Grev. and Balf. It differs chemically from the naturally occurring yellow flavonol, quercetin, by having two more hydrogen atoms in the molecule. The conversion of dihydroquercetin to quercetin in the laboratory is effected with hot dilute mineral acids or with bisulfite solutions.
在花旗松心材中发现了二氢槲皮素 （4），并且从花旗松树皮的软木部分 Pseudotsuga taxifolia （Poir.） 中获得的这种 20 % 20 % 20%20 \% 材料中的大部分都是从花旗松树皮的软木部分获得的。布里特。（7）. 在这个实验室中，它还从 Jeffrey 松的树皮中分离出来。和 Balf.它与天然存在的黄色黄酮醇槲皮素在化学上不同，因为分子中多了两个氢原子。在实验室中，二氢槲皮素转化为槲皮素是通过热的稀无机酸或亚硫酸氢盐溶液实现的。
Dihydroquercetin is white in color and crystallizes from hot aqueous solutions with water of crystallization that is lost upon heating at approximately 125 ∘ C 125 ∘ C 125^(@)C125^{\circ} \mathrm{C}. The solubility has been found to be 9.3 % 9.3 % 9.3%9.3 \% in boiling water and 0.51 % 0.51 % 0.51%0.51 \% in water at 15 ∘ C 15 ∘ C 15^(@)C15^{\circ} \mathrm{C}. The melting point of dihydroquercetin had been reported previously to be approximately 242 ∘ C 242 ∘ C 242^(@)C242^{\circ} \mathrm{C}. Recent work with large quantities of dihydroquercetin has shown that this melting point is too low. When the crude dihydroquercetin is recrystallized from boiling 0.5 % 0.5 % 0.5%0.5 \% sulfuric acid solution and then from boiling water containing a little decolorizing charcoal, the melting point is 252 to 253 ∘ C 253 ∘ C 253^(@)C253^{\circ} \mathrm{C}. as determined on a FischerJohns melting point block.
二氢槲皮素为白色，从热的水溶液中结晶，结晶水在加热 125 ∘ C 125 ∘ C 125^(@)C125^{\circ} \mathrm{C} 时损失约 .已发现溶解度在 9.3 % 9.3 % 9.3%9.3 \% 沸水中和 0.51 % 0.51 % 0.51%0.51 \% 水中。 15 ∘ C 15 ∘ C 15^(@)C15^{\circ} \mathrm{C} 先前曾报道过二氢槲皮素的熔点约为 242 ∘ C 242 ∘ C 242^(@)C242^{\circ} \mathrm{C} 。最近对大量二氢槲皮素的研究表明，该熔点太低。当粗二氢槲皮素从沸腾的 0.5 % 0.5 % 0.5%0.5 \% 硫酸溶液中再从含有少量脱色木炭的沸水中重结晶时，熔点为 252 至 253 ∘ C 253 ∘ C 253^(@)C253^{\circ} \mathrm{C} 。在 FischerJohns 熔点模块上测定。
Douglas fir is the major lumber, plywood, and pole and piling species in this country. The potential annual supply of Douglas fir bark is estimated to be in excess of two million tons. Recent analyses in this laboratory of Douglas fir bark taken from sawlogs are given in Table I. The analytical data show that a ton of such bark may contain from 80 to 152 pounds of dihydroquercetin.
花旗松是这个国家的主要木材、胶合板、杆子和桩树种。据估计，花旗松树皮的潜在年供应量将超过 200 万吨。表 I 给出了该实验室对从锯木中提取的花旗松树皮的最新分析。分析数据显示，一吨这样的树皮可能含有 80 到 152 磅的二氢槲皮素。
TABLE I  表 I
Analyses of Douglas Fir Bark from Sawlogs (Percentage of oven-dry weight of bark)
锯木花旗松树皮的分析（树皮的烘箱干重百分比）
Source of bark  树皮来源 Tannin  单宁 Waxes  蜡 Dihydroquercetin  二氢槲皮素
% % %
Rockport, California  加利福尼亚州罗克波特 8.8 6.5 6.0
Taos, New Mexico.  新墨西哥州陶斯。 13.6 9.2 7.6
Fall Creek, Oregon  俄勒冈州福尔克里克 7.3 10.2 4.0
Molalla, Oregon..................
俄勒冈州莫拉拉..................		 8.1 8.0 5.5
Source of bark Tannin Waxes Dihydroquercetin % % % Rockport, California 8.8 6.5 6.0 Taos, New Mexico. 13.6 9.2 7.6 Fall Creek, Oregon 7.3 10.2 4.0 Molalla, Oregon.................. 8.1 8.0 5.5| Source of bark | Tannin | Waxes | Dihydroquercetin | | :--- | :--- | :--- | :--- | | | % | % | % | | Rockport, California | 8.8 | 6.5 | 6.0 | | Taos, New Mexico. | 13.6 | 9.2 | 7.6 | | Fall Creek, Oregon | 7.3 | 10.2 | 4.0 | | Molalla, Oregon.................. | 8.1 | 8.0 | 5.5 |

Preparation of Dihydroquercetin
二氢槲皮素的制备

Dihydroquercetin may be obtained along with a small amount of reddish-brown tannin by re-extracting benzene extracted (wax-free) bark with ethyl ether or isopropyl ether. Also it may be obtained by re-extracting the solid or concentrated hot-water extracts from Douglas fir bark with either of these ethers. A crude reddish-brown crystalline product was usually obtained when the hot-water extract from the cork fraction of the bark was evaporated to dryness or when powdered hot-water extracts from the bark were re-extracted with acetone or other ketones.
通过用乙醚或异丙醚重新提取苯提取的（无蜡）树皮，可以得到二氢槲皮素和少量红棕色单宁。也可以通过用这些醚中的任何一种从花旗松树皮中重新提取固体或浓缩的热水提取物来获得。当树皮软木部分的热水提取物蒸发至干燥时，或者当树皮中的粉末状热水提取物用丙酮或其他酮重新提取时，通常会获得粗的红棕色结晶产品。
The dihydroquercetin used in this work was prepared from the hot-water extracts from Douglas fir bark by re-extraction with ethyl ether. Distillation of the ethyl ether left a light brown powder, which
本研究中使用的二氢槲皮素是由花旗松树皮的热水提取物通过乙醚重新提取制备的。乙醚蒸馏得到浅棕色粉末，
was further purified by recrystallization once from a hot 0.5 % 0.5 % 0.5%0.5 \% solution of sulfuric acid and then from boiling water that contained a little decolorizing charcoal. When purified in this manner, the product was obtained as white crystals having a melting point of 252 to 253 ∘ C 253 ∘ C 253^(@)C253{ }^{\circ} \mathrm{C}. If the recrystallization from dilute sulfuric acid was omitted, the product usually melted at 241 to 242 ∘ C 242 ∘ C 242^(@)C242^{\circ} \mathrm{C}.
通过从硫酸的热 0.5 % 0.5 % 0.5%0.5 \% 溶液中重结晶一次，然后从含有少量脱色木炭的沸水中进一步纯化。以这种方式纯化时，得到熔点为 252 至 253 ∘ C 253 ∘ C 253^(@)C253{ }^{\circ} \mathrm{C} 的白色结晶。如果省略稀硫酸的重结晶，则产物通常在 241 至 242 ∘ C 242 ∘ C 242^(@)C242^{\circ} \mathrm{C} 处熔化。
Crude dihydroquercetin also was purified by recrystallization from a hot sodium bisulfite solution. On cooling, the bisulfite addition compound separated as white crystals, which decomposed on heating at about 225 ∘ C 225 ∘ C 225^(@)C225^{\circ} \mathrm{C}. The free flavanone and some quercetin were recovered from the bisulfite compound upon acidification with dilute sulfuric acid. When recrystallized from hot water, the product had a melting point of 246 to 247 ∘ C 247 ∘ C 247^(@)C247^{\circ} \mathrm{C}.
粗二氢槲皮素也通过从热的亚硫酸氢钠溶液中重结晶来纯化。冷却时，亚硫酸氢盐加成化合物分离成白色晶体，加热时在约 225 ∘ C 225 ∘ C 225^(@)C225^{\circ} \mathrm{C} .用稀硫酸酸化后，从亚硫酸氢盐化合物中回收游离黄烷酮和一些槲皮素。用热水重结晶时，该产品的熔点为 246 至 247 ∘ C 247 ∘ C 247^(@)C247^{\circ} \mathrm{C} 。

Antioxidant Properties of Dihydroquercetin
二氢槲皮素的抗氧化特性

The antioxidant activity of dihydroquercetin and certain of its esters was determined on lard, cottonseed oil, and butter oil by methods similar to those used by other investigators ( 2 , 6 , 11 2 , 6 , 11 2,6,112,6,11 ). Weighed amounts of the lard or oils were placed in open glass containers and exposed to the atmosphere at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C}., 97.7 ∘ C 97.7 ∘ C 97.7^(@)C97.7^{\circ} \mathrm{C}., and at room temperature. A constant-temperature bath was used for the tests made at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C}. and 97.7 ∘ C 97.7 ∘ C 97.7^(@)C97.7^{\circ} \mathrm{C}. When lard samples were tested for stability at 97.7 ∘ C 97.7 ∘ C 97.7^(@)C97.7^{\circ} \mathrm{C}., a rapid stream of air was allowed to bubble through the samples. The procedure and apparatus recommended by the American Oil Chemists’ Society Committee on Analysis of Commercial Fats and Oils were used (1, 3, 10, 13). Changes in peroxide values were determined by the Henderson and Young modification (5) of the Wheeler method (14) as well as by the method recommended by the American Oil Chemists’ Society Committee on Analvsis of Commercial Fats and Oils (10). Each of these procedures gave the same peroxide value when applied to a given oil. Free fat acid tests were made in accordance with the method of The Association of Official Agricultural Chemists (9). Under the experimental conditions employed in these tests no appreciable change in free fat acid was noticed.
二氢槲皮素及其某些酯的抗氧化活性是通过类似于其他研究人员使用的方法在猪油、棉籽油和黄油上测定的 （ 2 , 6 , 11 2 , 6 , 11 2,6,112,6,11 ）。将称量的猪油或油放入敞开的玻璃容器中，并在 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} .、 97.7 ∘ C 97.7 ∘ C 97.7^(@)C97.7^{\circ} \mathrm{C} . 和 室温下暴露在大气中。恒温浴用于在 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 进行的测试。和 97.7 ∘ C 97.7 ∘ C 97.7^(@)C97.7^{\circ} \mathrm{C} .当猪油样品在 97.7 ∘ C 97.7 ∘ C 97.7^(@)C97.7^{\circ} \mathrm{C} . 下测试稳定性时，允许快速气流通过样品。使用了美国石油化学家协会商业油脂分析委员会推荐的程序和设备 （1， 3， 10， 13）。过氧化值的变化是通过 Wheeler 方法 （14） 的 Henderson 和 Young 修改 （5） 以及美国石油化学家协会商业油脂分析委员会 （10） 推荐的方法确定的。当应用于给定的油时，这些程序中的每一个都给出了相同的过氧化值。根据官方农业化学家协会 （9） 的方法进行游离脂肪酸测试。在这些测试中采用的实验条件下，没有注意到游离脂肪酸的明显变化。
Lard samples containing no antioxidant were obtained from local markets. Cottonseed oil, U. S. P., was procured from the School of Pharmacy, Oregon State College. This oil had been in storage for some time and had a golden color. Butter oil was prepared for this work by G. A. Richardson, Dairy Chemistry Laboratory, Oregon State College. No color was added to this oil, and its melting point was approximately 32 to 33 ∘ C 33 ∘ C 33^(@)C33^{\circ} \mathrm{C}.
不含抗氧化剂的猪油样本购自本地市场。棉籽油，U. S. P.，采购自俄勒冈州立学院药学院。这种油已经存放了一段时间，呈金黄色。黄油由俄勒冈州立大学乳品化学实验室的 G. A. Richardson 为这项工作制备。这种油没有添加任何颜色，其熔点约为 32 至 33 ∘ C 33 ∘ C 33^(@)C33^{\circ} \mathrm{C} 。
The antioxidant was added by mixing one ml . of an alcoholic solution of the antioxidant to 100 grams of the lard or oil. For the tests at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C}., 10 -gram samples of the control and the test specimens were placed in 25 mm . test tubes and then stored in the constant temperature bath whereas the samples tested at room temperature were placed in 250 − ml 250 − ml 250-ml250-\mathrm{ml}. Erlenmeyer flasks. In this way, for each temperature condition, the ratio of surface exposed to the air to the weight of the sample was constant. Samples were tested for per-
通过混合 1 ml 来添加抗氧化剂。抗氧化剂的酒精溶液与 100 克猪油或油。对于 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} . 的测试，将 10 克对照样品和测试样品置于 25 毫米中。试管，然后储存在恒温浴中，而在室温下测试的样品则置于 250 − ml 250 − ml 250-ml250-\mathrm{ml} 中。锥形瓶。这样，对于每种温度条件，暴露于空气中的表面与样品重量的比率是恒定的。对样品进行了 per-
oxide values, expressed as milliequivalents per kg. of fat, at recorded intervals.
氧化物值，以每公斤毫当量表示。的脂肪，以记录的时间间隔。
Lard. The effects of 0.015 , 0.03 , 0.06 0.015 , 0.03 , 0.06 0.015,0.03,0.060.015,0.03,0.06, and 0.1 % 0.1 % 0.1%0.1 \% of dihydroquercetin on the stability of lard are shown in Figure 1. Mixtures containing more than 0.03 % 0.03 % 0.03%0.03 \% dihydroquercetin were cloudy at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C}. The results indicate that the resistance of lard to oxidation increased as the proportion of dihydroquercetin was increased.
猪油。 0.015 , 0.03 , 0.06 0.015 , 0.03 , 0.06 0.015,0.03,0.060.015,0.03,0.06 和 0.1 % 0.1 % 0.1%0.1 \% 二氢槲皮素对猪油稳定性的影响如图 1 所示。含有超过 0.03 % 0.03 % 0.03%0.03 \% 二氢槲皮素的混合物在 时呈混浊状态。 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 结果表明，随着二氢槲皮素比例的增加，猪油的抗氧化性增加。
Fig. 1. Peroxide values of lard with different amounts of dihydroquercetin at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C}.
图 1.含不同量二氢槲皮素的猪油的过氧化值为 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 。
  1. 0.0 % 0.0 % 0.0%0.0 \% dihydroquercetin as control.
    0.0 % 0.0 % 0.0%0.0 \% 二氢槲皮素作为对照。
  2. 0.015 % 0.015 % 0.015%0.015 \% dihydroquercetin.
    0.015 % 0.015 % 0.015%0.015 \% 二氢槲皮素。
    3.0 .030 % 3.0 .030 % 3.0.030%3.0 .030 \% dihydroquercetin.
    3.0 .030 % 3.0 .030 % 3.0.030%3.0 .030 \% 二氢槲皮素。
  3. 0.060 % 0.060 % 0.060%0.060 \% dihydroquercetin.
    0.060 % 0.060 % 0.060%0.060 \% 二氢槲皮素。
  4. 0.100 % 0.100 % 0.100%0.100 \% dihydroquercetin.
    0.100 % 0.100 % 0.100%0.100 \% 二氢槲皮素。
This same lard sample was subjecetd to the fat stability test by the active oxygen method recommended by the Committee on Analysis of Commercial Fats and Oils (10). The results shown in Table II are in agreement with the results shown in Figure 1.
同样的猪油样品通过商业油脂分析委员会推荐的活性氧法进行脂肪稳定性测试 （10）。表 II 中显示的结果与图 1 中显示的结果一致。
A study of the comparative antioxidant effects of dihydroquercetin and quercetin on lard was made, and the results are given in Figure 2. The peroxide values indicate that quercetin has a greater antioxidant activity than dihydroquercetin. Quercetin however has the disadvantage of giving a yellow tint to lard.
对二氢槲皮素和槲皮素对猪油的抗氧化作用进行了比较研究，结果如图 2 所示。过氧化值表明槲皮素比二氢槲皮素具有更大的抗氧化活性。然而，槲皮素的缺点是使猪油呈黄色。
TABLE II  表 II
Effect of Dihydroquercetin on the Stability of Lard at 97.7 ∘ C 97.7 ∘ C 97.7^(@)C97.7^{\circ} \mathrm{C}.
二氢槲皮素对猪油稳定性的影响 97.7 ∘ C 97.7 ∘ C 97.7^(@)C97.7^{\circ} \mathrm{C} 。
Mixture  混合物 Stability (A.O.M)  稳定性 （A.O.M）
Hrs.  小时。
Control.  控制。 5
Lard + 0.015% dihydroque-cetin...........................
猪油 + 0.015% 二氢啉油素...........................		 16
Lard + 0.03%  猪油 + 0.03% 4.3
Lard + 0.06%  猪油 + 0.06% 79
Effect of Dihydroquercetin on the Stability of Lard at 97.7^(@)C. Mixture Stability (A.O.M) Hrs. Control. 5 Lard + 0.015% dihydroque-cetin........................... 16 Lard + 0.03% 4.3 Lard + 0.06% 79| Effect of Dihydroquercetin on the Stability of Lard at $97.7^{\circ} \mathrm{C}$. | | | :--- | :--- | | Mixture | Stability (A.O.M) | | | Hrs. | | Control. | 5 | | Lard + 0.015% dihydroque-cetin........................... | 16 | | Lard + 0.03% | 4.3 | | Lard + 0.06% | 79 |
Fig. 2. Peroxide values of lard with dihydroquercetin and quercetin at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C}.
图 2.猪油与二氢槲皮素和槲皮素的过氧化值为 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 。
  1. 0.0 % 0.0 % 0.0%0.0 \% antioxidant as control.
    0.0 % 0.0 % 0.0%0.0 \% 抗氧化剂作为对照。
  2. 0.030 % 0.030 % 0.030%0.030 \% dihydroquercetin.
    0.030 % 0.030 % 0.030%0.030 \% 二氢槲皮素。
  3. 0.030 % 0.030 % 0.030%0.030 \% quercetin.   0.030 % 0.030 % 0.030%0.030 \% 槲 皮 素。
The effect of adding citric acid and dihydroquercetin to lard is shown in Figure 3. In this experiment the peroxide values of lard a) without an antioxidant, b) with 0.015 % 0.015 % 0.015%0.015 \% dihydroquercetin and 0.015 % 0.015 % 0.015%0.015 \% of citric acid, and c ) with 0.03 % 0.03 % 0.03%0.03 \% of dihydroquercetin were determined. The experimental results indicate that citric acid enhances the antioxidant activity of dihydroquercetin in lard.
向猪油中添加柠檬酸和二氢槲皮素的效果如图 3 所示。在该实验中，测定了猪油 a） 不含抗氧化剂，b） 含 0.015 % 0.015 % 0.015%0.015 \% 二氢槲皮素和 0.015 % 0.015 % 0.015%0.015 \% 柠檬酸，以及 c） 含 0.03 % 0.03 % 0.03%0.03 \% 二氢槲皮素的过氧化物值。实验结果表明，柠檬酸增强了猪油中二氢槲皮素的抗氧化活性。
The lard sample used for the experiment on the synergistic action of citric acid at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C}. was also tested by the active oxygen method (10). The results are shown in Table III.
用于柠檬酸协同作用实验的猪油样品。 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 也通过活性氧法 （10） 进行了测试。结果如表 III 所示。
TABLE III  表 III
Stability of Lard with Citric Acid and Dihydroquercetin
柠檬酸和二氢槲皮素的猪油稳定性
Mixture  混合物 Stability (A. O. M.)
稳定性 （A. O. M.）
Hrs.  小时。
Control  控制 4.5
Lard + 0.015% dihydroquercetin.
猪油 + 0.015% 二氢槲皮素。		 18.0
Lard + 0.015% each of dihydroquercetin and citric acid
猪油 + 二氢槲皮素和柠檬酸各 0.015%		 34.0
Lard + 0.03% dihydroquercetin
猪油 + 0.03% 二氢槲皮素		 41.0
Lard + 0.03% each of dihydroquercetin and citric acid.......
猪油 + 二氢槲皮素和柠檬酸各 0.03%.......		 57.0
Mixture Stability (A. O. M.) Hrs. Control 4.5 Lard + 0.015% dihydroquercetin. 18.0 Lard + 0.015% each of dihydroquercetin and citric acid 34.0 Lard + 0.03% dihydroquercetin 41.0 Lard + 0.03% each of dihydroquercetin and citric acid....... 57.0| Mixture | Stability (A. O. M.) | | :--- | :--- | | | Hrs. | | Control | 4.5 | | Lard + 0.015% dihydroquercetin. | 18.0 | | Lard + 0.015% each of dihydroquercetin and citric acid | 34.0 | | Lard + 0.03% dihydroquercetin | 41.0 | | Lard + 0.03% each of dihydroquercetin and citric acid....... | 57.0 |
It has been reported that tests by the active oxygen method show no constant relationship between the stability of lard and storage at room temperature (12). The lard stability tests with different quantities of dihydroquercetin therefore were repeated at room temperature ( 20 to 30 ∘ C 30 ∘ C 30^(@)C30^{\circ} \mathrm{C}.). In the latter tests 10.0 ± 0.01 10.0 ± 0.01 10.0+-0.0110.0 \pm 0.01 grams of the lard mixtures were placed in 250 − ml 250 − ml 250-ml250-\mathrm{ml}. Erlenmeyer flasks and stored away from dust in a cabinet. The ratio of surface to weight was 5.0 sq . cm 5.0 sq . cm 5.0sq.cm5.0 \mathrm{sq} . \mathrm{cm}. per gram. Peroxide values were deter-
据报道，活性氧法的测试表明，猪油的稳定性与室温下储存之间没有恒定的关系 （12）。因此，在室温（20 至 30 ∘ C 30 ∘ C 30^(@)C30^{\circ} \mathrm{C} .）下重复使用不同量的二氢槲皮素进行猪油稳定性测试。在后一项测试 10.0 ± 0.01 10.0 ± 0.01 10.0+-0.0110.0 \pm 0.01 中，将克猪油混合物放入 250 − ml 250 − ml 250-ml250-\mathrm{ml} 中。锥形瓶并存放在远离灰尘的橱柜中。表面与重量的比值为 5.0 sq . cm 5.0 sq . cm 5.0sq.cm5.0 \mathrm{sq} . \mathrm{cm} 。每克。过氧化值被阻止
Fig. 3. Peroxide values of citric acid and dihydroquercetin in lard at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C}.
图 3.猪油中柠檬酸和二氢槲皮素的过氧化值为 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 。
  1. 0.0% antioxidant as control.
    0.0% 抗氧化剂作为对照。
  2. 0.030% dihydroquercetin.
    0.030% 二氢槲皮素。
  3. 0.015 % 0.015 % 0.015%0.015 \% citric acid and 0.015 % 0.015 % 0.015%0.015 \% dihydroquercetin.
    0.015 % 0.015 % 0.015%0.015 \% 柠檬酸和 0.015 % 0.015 % 0.015%0.015 \% 二氢槲皮素。
Fig. 4. Peroxide values of lard at room teniperature.
图 4.猪油在室温下的过氧化值。
  1. 0.0 % 0.0 % 0.0%0.0 \% dihydroquercetin as control.
    0.0 % 0.0 % 0.0%0.0 \% 二氢槲皮素作为对照。
  2. 0.030 % 0.030 % 0.030%0.030 \% dihydroquercetin.
    0.030 % 0.030 % 0.030%0.030 \% 二氢槲皮素。
  3. 0.060 % 0.060 % 0.060%0.060 \% dihydroquercetin.
    0.060 % 0.060 % 0.060%0.060 \% 二氢槲皮素。
  4. 0.100 % 0.100 % 0.100%0.100 \% dihydroquercetin.
    0.100 % 0.100 % 0.100%0.100 \% 二氢槲皮素。
    mined over a period of 196 days, and the results are shown in Figure 4.
    开采了 196 天，结果如图 4 所示。
Butter Oil and Cottonsced Oil. The initial peroxide value of the sample of cottonseed oil on hand was greater than expected. However the effect of dihydroquercetin on the stability of this oil was found similar to that for lard as is shown in Figure 5. The
Butter Oil 和 Cottonsced Oil。手头棉籽油样品的初始过氧化值高于预期。然而，发现二氢槲皮素对这种油稳定性的影响与猪油相似，如图 5 所示。这
Fig. 5. Peroxide values of dilydroquercetin in cottonseed oil at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C}.
图 5.棉籽油中二 lydroquercetin 的过氧化值为 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 。
  1. 0.0 % 0.0 % 0.0%0.0 \% dihydroquercetin as control.
    0.0 % 0.0 % 0.0%0.0 \% 二氢槲皮素作为对照。
  2. 0.100 % 0.100 % 0.100%0.100 \% dibydroquercetin.
    0.100 % 0.100 % 0.100%0.100 \% Dibydroquercetin.
    sample of butter oil contained a considerable amount of natural antioxidant. Several 10 ± 0.01 − gram 10 ± 0.01 − gram 10+-0.01-gram10 \pm 0.01-\mathrm{gram} samples, in the presence of and in the absence of dihydroquercetin and citric acid, were tested. The results are shown in Figure 6.
    黄油样本含有相当数量的天然抗氧化剂。在存在和不存在二氢槲皮素和柠檬酸的情况下，测试了几个 10 ± 0.01 − gram 10 ± 0.01 − gram 10+-0.01-gram10 \pm 0.01-\mathrm{gram} 样品。结果如图 6 所示。
At the start of this experiment the control as well as the butter oil containing dihydroquercetin and citric acid had a golden appearance. At the end of 350 hours of incubation at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C}. the golden color of the control samples faded considerably, and at the end of 568 hours these samples were colorless. On the other hand, the sample in the presence of dihydroquercetin and citric acid retained its original golden color, as viewed with the naked eye. The change of color of butter oil is an indication of the end of its induction period.
在该实验开始时，对照以及含有二氢槲皮素和柠檬酸的黄油均呈金黄色。在 孵育 350 小时结束时。 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 对照样品的金黄色明显褪色，在 568 小时结束时，这些样品呈无色状态。另一方面，样品在二氢槲皮素和柠檬酸存在下保持了肉眼可见的原始金色。黄油颜色的变化表明其诱导期结束。

Esters of Dihydroquercetin
二氢槲皮素酯

The acetyl, propionyl, and benzoyl esters of dihydroquercetin were prepared and tested for antioxidant activity. The pentaacetate was prepared with acetic anhydride and prridine and had a melting point of 86 to 88 ∘ C 88 ∘ C 88^(@)C88^{\circ} \mathrm{C}. When the dihydroquercetin was similarly treated with propionic anhrdride and pyridine, the pentapropionate was obtained with a melting point of 46 to 48 ∘ C 48 ∘ C 48^(@)C48^{\circ} \mathrm{C}. The pentabenzoate was prepared with benzoyl chloride and pyridine and had a melting point of 108 to 110 ∘ C 110 ∘ C 110^(@)C110^{\circ} \mathrm{C}. It was found that none of
制备二氢槲皮素的乙酰基、丙酰基和苯甲酰酯，并测试抗氧化活性。用乙酐和吡啶制备五乙酸酯，熔点为 86 至 88 ∘ C 88 ∘ C 88^(@)C88^{\circ} \mathrm{C} 。当二氢槲皮素用丙酸甘菊酯和吡啶进行类似处理时，得到熔点为 46 至 48 ∘ C 48 ∘ C 48^(@)C48^{\circ} \mathrm{C} 的五丙酸盐。用苯甲酰氯和吡啶制备五苯甲酸盐，熔点 108 至 110 ∘ C 110 ∘ C 110^(@)C110^{\circ} \mathrm{C} 。结果发现，没有
  1. 1 1 ^(1){ }^{1} Oregon Forest Products Laboratory and Department of Chemistry, Oregon State College, Corvallis, Ore.
    1 1 ^(1){ }^{1} 俄勒冈州立学院俄勒冈州林产品实验室和化学系，俄勒冈州科瓦利斯。
    2 2 2 2 _(2)^(2){ }_{2}^{2} Oregon Forest Products Laboratory, Corvallis, Ore,
    2 2 2 2 _(2)^(2){ }_{2}^{2} 俄勒冈州林产品实验室，俄勒冈州科瓦利斯，