Saponins Esculeosides B-1 and B-2 in Italian Canned Tomatoes

Abstract

Italian canned tomatoes contain the tomato glycosides esculeosides B-1 (1, 0.0052%) and B-2 (2, 0.0068%) without esculeoside A. Herein, the structure of esculeoside B-1 (1) is characterized to be 3-O-β-lycotetraosyl (5S,22R,23S,25S)-22,26-epimino-16β,23-epoxy-3β,23,27-trihydroxycholestane 27-O-β-d-glucopyranoside. We hypothesized that these substances might be derived from esculeoside A when the cans are prepared with treatment in boiling water. To confirm that hypothesis, we refluxed esculeoside A with water for 6.5 h, providing esculeosides B-1 (1) and B-2 (2) in yields of 25.8% and 31.0%, respectively. Key words Solanum lycopersicum; canned tomato; tomato saponin; esculeoside A; esculeoside B-1; esculeoside B-2In 2003, Nohara and colleagues 1,2) isolated a tomato saponin, called esculeoside A, from the ripe fruits of tomato, Solanum lycopersicum L. and determined its structure ( Fig. 1). Tomato saponin is a significant component of ripened tomatoes and occurs at levels approximately 4-fold higher than those of lycopene. Thus far, the bioactivity of tomato has been attributed solely to lycopene. Therefore, carrying out pharmacological examinations of esculeoside A in the near future is important.Recently, Fujiwara et al. 3) have revealed that oral administration of esculeoside A to apolipoprotein E-deficient mice significantly reduces levels of serum cholesterol glycerides, low-density lipoprotein-cholesterol and the areas of atherosclerotic lesions without any detectable side effects. Our recent studies on the constituents of Solanum plants have revealed that pregnane glycosides are accompanied by normal spirostanol and furostanol glycosides [4][5][6][7][8][9][10][11][12] ; esculeogenin A is easily converted into a pregnane derivative by refluxing with aqueous pyridine, 13) and pregnane glycoside has been obtained from the over-ripe tomato fruit. 14) These facts strongly suggest that orally administered steroidal glycosides can be metabolized into pregnane derivatives, which are a type of steroidal hormone.Therefore, in further experiments, men consumed tomatoes and their urine was collected and separated with various column chromatographies to afford 3 androstane derivatives. 15)These androsterone analogs are normally excreted; however, because no excretions were detected in the control samples, the occurrence of androsterone analogs indicated excretion via the production of progesterone by subjects that had consumed tomatoes. The tomato steroidal glycoside might stimulate the hormone secretor or perhaps is itself metabolized into the pregnane. We hypothesize that orally administered steroidal glycosides such as spirostanol, furostanol and spirosolane glycosides are metabolized, introducing a hydroxyl group at C-23. These intermediates may then be metabolized into pregnane derivatives.Thus, we conclude that the tomato saponin esculeoside A

Saponins, Esculeosides B-1 and B-2, in Tomato Juice and Sapogenol, Esculeogenin B₁

“…The configuration of the hydroxyl group at C-23 was estimated as β-axial because the H 3 -21 signals stayed at δ 1.26 in the usual chemical shift, whereas it appeared at δ 1.59 in a 1,3-diaxial correlation 11) with the C-23-OH group in esculeogenin B 2 (5). Therefore, the structure of 4 could be represented as (5α,22S,23S,25S)-22,26-epimino-16β,23-epoxy-3β,23,27-trihydroxycholestane, and the configuration at C-22 in esculeoside B-1 (2) 8) should be revised to S from R. Thus, we have shown that tomato juices packaged in plastic bottles contain tomato saponins, esculeosides B-1 (2) and B-2 (3), which provide esculeogenins B 1 (4) and B 2 (5), respectively, by 2 N HCl hydrolysis. We concluded that tomato saponins in juice packaged in plastic bottles were derived from esculeoside A (1) when the juiceis processed with boiling water.…”

“…Such tomatoes contain tomato saponins, rare, naturally occurring steroidal solanocapsinetype glycosides, a 0.095% mixture of esculeosides B-1 (2) and B-2 (3) lacking esculeoside A (1). 8) We refluxed esculeoside A (1) with water for 6.5 h, providing a mixture of esculeosides B-1 (2) and B-2 (3) quantitatively; therefore, we hypothesized that these substances might be derived from esculeoside A (1) when the cans are processed with boiling water. 8) In the present study, we analyzed the amount of tomato saponin in tomato juice commercially processed in 900 g plastic bottles to compare the respective ingredients in each bottles.…”

“…8) We refluxed esculeoside A (1) with water for 6.5 h, providing a mixture of esculeosides B-1 (2) and B-2 (3) quantitatively; therefore, we hypothesized that these substances might be derived from esculeoside A (1) when the cans are processed with boiling water. 8) In the present study, we analyzed the amount of tomato saponin in tomato juice commercially processed in 900 g plastic bottles to compare the respective ingredients in each bottles. Five kinds juice produced by different companies were individually treated and passed through highly porous polystyrene gel (Diaion HP-20), and the resulting methanol residue was then subjected to dextran gel (Sephadex LH-20) column chromatography, and then eluted with 90% methanol.…”

“…We recognized that the esculeoside A in fresh tomato converts to esculeosides B-1 (2) and B-2 (3) when these tomatoes are packed in bottles via sterilization with boiling water similar to that in canned preparation. 8) Next, a mixture of esculeosides B-1 (2) and B-2 (3) obtained from juice was separated with octadecylsilane (ODS) to give two saponins. Esculeoside B-2 (3) was hydrolyzed by refluxing with 2 N HCl for 1 h to obtain a sapogenol, esculeogenin B 2 (5) as colorless needles, melting point (mp) 223-226°C (decomp), which was identical to the esculeogenin B previously reported.…”

Conversion of Tomato Saponins to Pregnane Derivatives

“…Furthermore, we found a new method for the respective conversions of 1 or a mixture of esculeosides B-1 (2) and B-2 (3) 6) to the pregnane derivative as follows: Esculeoside A (1) was refluxed in 1 N KOH for 1 h. The reaction mixture was separated by silica gel column chromatography using a mixture of CHCl 3 -MeOH-H 2 O (8 : 2 : 0.2) to afford the major product (4) On the other hand, a mixture of esculeoside B-1 (2) and esculeoside B-2 (3) was refluxed in 1 N KOH for 1 h. After neutralizing with 1 N HCl, the reaction mixture was concentrated under reduced pressure and passed through Diaion HP-20 to afford the crude material, which was purified by using silica gel chromatography using a mixture of Next, compound 4 was refluxed in 2 N HCl-MeOH for 1 h, and the resulting reaction mixture was purified by silica gel column chromatography using a mixture of n-hexane-acetone H-NMR spectrum (in CDCl 3 ) showed three methyl groups at δ 0.77 (3H, s), 0.81 (3H, s), and 2.18 (3H, s); an oxygen-bearing methane proton at δ 3.53 (1H, m); and an olefinic proton at δ 6.62 (1H, dd, J=1.8, 3.1 Hz). Moreover, the 13 C-NMR spectrum showed a total of 21 carbons including three methyl groups at δ 12.2, 15.9, and 28.5; one oxygen-bearing methine carbon at δ 71.3; two olefinic carbons at δ 144.4 and 155.5; and a carbonyl carbon at δ 196.8.…”