EXPERIMENTAL
General. UV spectra of proanthocyanidines and their derivatives were recorded in alcohol solution on a
Perkin—Elmer-Lambda-16 instrument; IR spectra, on a Perkin—Elmer-2000 FT-IR instrument in KBr pellets. 1H and 13
NMR spectra were obtained on a Tesla BS-567A/100 (1H) and 25 (13C) instrument in (CD ) CO—D O (1:1) solution with TMS
C
3 2
2
as internal standard (δ-scale). The molecular weight was determined in a MOM 3170 ultracentrifuge and by gel filtration over
a calibrated column of Sephadex LH-20; the optical activity, on a JASCO-J-20 instrument. The purity of the compounds was
determined using paper chromatography and TLC over Silufol UV-254 plates [2] using vanillin (1%) in alcoholic H SO (5-
2
4
10%) as developer.
Extraction and Isolation of Proanthocyanidines. Bark of Z. jujuba (5.8 kg) was extracted six times with ethanol
(80%). The extracts were combined and evaporated in vacuo at 40°C to 2 L. The condensed extract was treated successively
with diethylether, ethylacetate, and n-butanol to give extracts of 18.2, 21.1, and 165 g, respectively. High-molecular-weight
proanthocyanidines (510 g) were isolated from the aqueous remainder.
Separation of Proanthocyanidines. The butanol extract (85 g) was mixed with cellulose (85 g), placed on a column
of microcrystalline cellulose (800 g), and eluted by CHCl —ethylacetate (1:10-1:20), ethylacetate, and acetone to give fractions
3
of 100 mL. The elution was monitored using TLC. Eluates 80-196 contained a mixture of relatively low-molecular-weight
proanthocyanidines, were combined, evaporated, and rechromatographed (41.9 g) over cellulose with elution by ethylacetate
and ethylacetate—acetone (10:1-1:1).
Compound 1. Solid from fractions 131-158 (1.325 g) was chromatographed over Sephadex LH-20 with elution by
ethanol (60%). Yield 1.213 g of amorphous substance, C75H62O31, mol. wt. 1458, [α]D24 +76.5° (c 1.0, acetone—water, 1:1).
Table 1 contains the 13C NMR data.
Base Cleavage of 1. Compound 1 (50 mg) was cleaved by the literature method [3]. Phloroglucinol, p-
hydroxybenzoic, protocatechuic, and gallic acids were detected and identified.
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Acid Cleavage of 1. Compound 1 (150 mg) produced (+)-catechin {mp 178-179°C, [α]D +18.3° (c 0.9,
acetone—water, 1:1)} and the anthocyanidines: cyanidin [R 0.69 (2 N HCl), λmax 552 (0.1% HCl in ethanol)], delphinidin
f
[R 0.36 (2 N HCl), λmax 554 nm (0.1% HCl in ethanol)], and pelargonidin [R 0.80 ( 2 N HCl), λmax 518 nm (0.1% HCl in
f
f
ethanol)].
Thiolytic Cleavage of 1. Compound 1 (350 mg) was cleaved and the products purified as before [1] to give
(+)-catechin (7 mg) and a mixture of thioesters (259 mg). The thioesters (200 mg) were mixed with ethanol—acetic acid
(9:1, 12 mL) and treated with Raney nickel catalyst at 50°C for 1 h. The reaction mixture was filtered. The filtrate was
condensed and chromatographed over Sephadex LH-20 with elution by ethanol (80%) to give (-)-epiafzelechin {mp 249-250°C,
[α]D22 -52° (c 1.0, acetone)}, (-)-epigallocatechin (mp 241-243°C, [α]D24 -69°), and (+)-catechin.
REFERENCES
1.
2.
3.
A. Malik, Z. A. Kuliev, U. A. Akhmedov, A. D. Vdovin, and N. D. Abdullaev, Khim. Prir. Soedin., 221 (1997).
A. B. Makhmatkulov, Z. A. Kuliev, A. D. Vdovin, and V. M. Malikov, Khim. Prir. Soedin., 233 (1994).
K. K. Kim, Z. A. Kuliev, A. D. Vdovin, M. R. Yagudaev, and V. M. Malikov, Khim. Prir. Soedin., 771 (1991).
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