商品描述

乳香酸(萃取液)

Common name : Olibanum, Frankincense,Salai gugal

Family : Burseraceae

Part used : Gum

Key applications : Anti-inflammatory, Antiarthritic.

Phytochemistry:

Boswellia serrata Gum contains a volatile oil, a range of triterpene acids viz. ß-Boswellic acids, Acetyl-ß-boswellic acid, keto -ß-boswellic acid which have been responsible its medicinal value. The crude gum contains: uronic acid anhydride, 20; nitrogen, 3.2; and inorganic oxides, 4.5%.

The purified gum gave: pentosans, 18.9; uronic acid, 30.9; and methoxyl groups, 3.6%.

On hydrolysis, the purified gum yielded: D-galactose, 46.2; D-arabinose, 11.7; D-xylose, 6.7; D-mannose, 4.5; and uronic acid anhydride, 30.9%.

Boswellic acids (b-boswellic acid):

Analysis of the non-volatile fraction (gum-rosin) of the oleo-gum- resin yielded a new diterpenic alcohol, serratol [C20H30O,b p 150° (bath)/1 mm], a-amyrin, ß-amyrin, methylchavicol, and eight triterpenic acids, viz., 3-a-acetoxytirucall-8, 24-dien-21-oic acid (C32H50O4, m p 220°), 3-ketotirucall-8,24-dien-21-oic acid(C30H46O3,m p 212°), 3-a-hydroxytirucall-8,24-dien-21-oic acid, 3ß-hydroxytirucall-8,24-dien-21-oic acid(C30H48O3, m p 198°),ß-boswellic acid,acetyl-ß-boswellic acid (C32H50O4, m p 253°), acetyl-11-keto-ß-boswellic acid (C32H48O5, m p 271°) and 11-keto-ß-boswellic acid(C30H46O4, m p 195°)(Pardhy & Bhattacharyya, Indian J Chem , 1978, 16B , 171, 174, 176). Many arylidene and pyrazoline derivatives were obtained from 3-keto-methyl-ß-boswellic ester isolated from the mixture of boswellic acids.

Workup-Dependent Formation of 5-Lipoxygenase Inhibitory Boswellic Acid Analogues:

Abstract:

Pentacyclic triterpenes from the 11-keto-boswellic acid series were identified as the active principal ingredients of Boswellia resin, inhibiting the key enzyme of leukotriene biosynthesis, 5-lipoxygenase (5-LO). Of the genuine boswellic acids hitherto characterized, 3-O-acetyl-11-keto--boswellic acid, AKBA (1), proved to be the most potent inhibitor of 5-LO. In the course of purification of further boswellic acid derivatives from Boswellia resin, we observed the degradation of the natural compound 3-O-acetyl-11-hydroxy--boswellic acid (2) to the thermodynamically more stable product 3-O-acetyl-9,11-dehydro--boswellic acid (4). The metastable intermediate of this conversion, under moderate conditions of workup in methanolic solutions, was identified as 3-O-acetyl-11-methoxy--boswellic acid (3). The novel artifactual boswellic acid derivatives inhibited 5-LO product formation in intact cells with different characteristics: 4 almost totally abolished 5-LO activity, with an IC50 of 0.75 M, whereas 3 and 9,11-dehydro--boswellic acid (5), the deacetylated analogue of 4, were incomplete inhibitors. The data suggest that the conditions chosen for the workup of Boswellia extracts could significantly influence the potency of their biological actions and their potential therapeutic effectiveness.

Two other pentacyclic triterpenic acids have also been isolated:

a-Boswellic Acid (V)

g-Boswellic Acid (VI)

Analysis of Boswellin (ref 6):

The following observations from the structural profiles of the pentacyclic triterpenic acids are analytically significant:

• All these compounds have a hydroxyl functional group either in free form (OH) or as acetate (OAc) in the "3" position and a carboxyl functional group (COOH) in the "4" position.

• Two of these acids have a keto (C=O) functional group in the "11" position, adjacent to the vinylic double bond.

• One boswellic acid can be transformed to another by simple chemical reactions.

The standard assay procedure for the acid fraction of Boswellia serrata extract involves:

• Titration - for total organic acids (I-X)

• A recently developed HPLC procedure for quantifying the four biologically active b-boswellic acids (I-IV)

Pioneering efforts by Sabinsa Corporation have resulted in improved methods for isolation and HPLC assay of the individual b-boswellic acids. Working HPLC standards for individual boswellic acids have also been meticulously prepared.

This involves the following steps:

• Physical separation of the mixture into individual components

• Elution of the separated components from the chromatographic column at different rates.

• Using UV detector, only the eluted components (one particular compound at a time) is quantitated. The peaks for b-Boswellic Acidand Acetyl-b-Boswellic Acid are recorded at 210 nm, while those for 11-keto-b-Boswellic Acid and Acetyl-11-keto-b-Boswellic Acid are recorded at 254 nm. Detection at two different UV absorptions are necessitated because of the spectral properties of the four compounds and their interactions.

This procedure ensures that each component is quantitated separately. The working standards used for comparison are characterized on the basis of measured physical and chemical properties.

Typical analytical results for a sample of Boswellin:

A. b-boswellic acids BY HPLC*

Figure 1 : Biological activity of various b-Boswellic acids in inhibiting the enzyme 5-Lipoxygenase

Composition of Commercial Samples : Comparative Evaluation:

Commercial samples of Boswellia serrata extracts from various sources were tested for b-Boswellic acids content and composition using HPLC methods. There are many companies offering Boswellia serrata extracts, ranging in potency from 50% to 100% boswellic acids. The analytical results for a few samples are indicated in Figure 2 and Figure 3, in terms of content and composition, respectively. In many commercial samples, the most active b-Boswellic acids are available in negligible quantities only.

Figure 2 : b-Boswellic acids Content in Commercial Samples of Boswellia serrata extract as determined by HPLC

Figure 3 : b-Boswellic acids Composition in Commercial Samples of Boswellia serrata extract as determined by HPLC

The total organic acids content in these samples as determined by titration is indicated in Figure 4.

Figure 4 : Total Organic Acids in Commercial Samples of Boswellia serrata extract as determined by titration 。

Thus it is evident that the active components in Boswellia serrata extract cannot be accurately predicted based on titrimetric method analysis. It is equally interesting to note that while the titrimetric method gives more than 50% organic acids, several of the commercially available products contain only negligible amounts of the two key boswellic acids, namely 11- keto- beta- and acetyl- 11- keto- beta- boswellic acids (Figure 3). These compounds are pharmacologically the more potent anti-inflammatory compounds.

Standard HPLC chromatograms for the four b-Boswellic acids are shown in Figures 5 and 6:

Figure 5: HPLC CHROMATOGRAM OF b-BOSWELLIC ACIDS WORKING STANDARD AT 210 nm

RT : 17.213	b-Boswellic acid
RT : 25.278	Acetyl- b-Boswellic acid

Figure 6: HPLC CHROMATOGRAM OF b-BOSWELLIC ACIDS WORKING STANDARD AT 254 nm

RT : 7.393	11-keto-b-Boswellic acid
RT : 10.835	Acetyl- 11-keto-b-Boswellic acid

b-Boswellic Acid

1. Chemical structure:
2. Chemical name	3a-Hydroxy- urs-12-en-23-oic acid
3. Molecular formula	C30H48O3
Molecular weight	456.7
4. Melting point	226 - 2280C (Lit. mp 228 - 230OC)
5. Specific rotation	+ 106.80 (Lit. + 108O)
6. FTIR (in KBr)	3500 cm-1, (OH) 1699.5 cm-1, (COOH)
7. UV (methanol)	Maxima at 208 nm (Lit. 208 nm)
8. NMR (in CDCl3)	5.15 (CH=C, vinylic proton) 4.08 (CH-OH) 2.3-1.1 (Methylenes and methines 23 protons) 1.1-0.7 (Methyls, 21 protons)
9. GC-MS	394 (M-68[44 due to-CO2 & 18 due to –H2O]) 218.
	Other characteristic fragments: 203, 189, 175, 161.

In another pioneering study4 using isolated boswellic acids, Y. Shao and others also showed that the pharmacological properties reside only in the four b-boswellic acids. This study focused on the anti-cancer activity of the isolated boswellic acids. Studies by H. Safayhi et al5 showed that Acetyl-11-keto-b-boswellic acid decreased the activity of human leukocyte elastase (HLE) in vitro with an IC50 value of about 15 mM.

In conclusion, the total acid value of the extract is useful as a standardization tool, while sophisticated analytical methodology should be used to determine the actual amount of therapeutically useful pentacyclic triterpenic acids, the b- boswellic acids.

Fig. 1. Chemical structures of the pentacyclic triterpenes used in the present study A) -boswellic acid; B) AKBA; C) -amyrin; D) -amyrin; E) 18 -glycyrrhetinic acid; F) ursolic acid).

Boswellic acid