Boswellia serrata: an overall assessment of in vitro, preclinical, pharmacokinetic and clinical data

Non-steroidal anti-inflammatory drug (NSAID) intake is associated with high prevalence of gastrointestinal or cardiovascular adverse effects. All efforts to develop NSAIDs that spare the gastrointestinal tract and the cardiovasculature are still far from achieving a breakthrough. In the last two decades, preparations of the gum resin of Boswellia serrata (a traditional ayurvedic medicine) and of other Boswellia species have experienced increasing popularity in Western countries. Animal studies and pilot clinical trials support the potential of B. serrata gum resin extract (BSE) for the treatment of a variety of inflammatory diseases like inflammatory bowel disease, rheumatoid arthritis, osteoarthritis and asthma. Moreover, in 2002 the European Medicines Agency classified BSE as an 'orphan drug' for the treatment of peritumoral brain oedema. Compared to NSAIDs, it is expected that the administration of BSE is associated with better tolerability, which needs to be confirmed in further clinical trials. Until recently, the pharmacological effects of BSE were mainly attributed to suppression of leukotriene formation via inhibition of 5-lipoxygenase (5-LO) by two boswellic acids, 11-keto-β-boswellic acid (KBA) and acetyl-11-keto-β-boswellic acid (AKBA). These two boswellic acids have also been chosen in the monograph of Indian frankincense in European Pharmacopoiea 6.0 as markers to ensure the quality of the air-dried gum resin exudate of B. serrata. Furthermore, several dietary supplements advertise the enriched content of KBA and AKBA. However, boswellic acids failed to inhibit leukotriene formation in human whole blood, and pharmacokinetic data revealed very low concentrations of AKBA and KBA in plasma, being far below the effective concentrations for bioactivity in vitro. Moreover, permeability studies suggest poor absorption of AKBA following oral administration. In view of these results, the previously assumed mode of action - that is, 5-LO inhibition - is questionable. On the other hand, 100-fold higher plasma concentrations have been determined for β-boswellic acid, which inhibits microsomal prostaglandin E synthase-1 and the serine protease cathepsin G. Thus, these two enzymes might be reasonable molecular targets related to the anti-inflammatory properties of BSE. In view of the results of clinical trials and the experimental data from in vitro studies of BSE, and the available pharmacokinetic and metabolic data on boswellic acids, this review presents different perspectives and gives a differentiated insight into the possible mechanisms of action of BSE in humans. It underlines BSE as a promising alternative to NSAIDs, which warrants investigation in further pharmacological studies and clinical trials.     

Preparation of Novel Analogues of the Nonredox-Type Non-Competitive Leukotriene Biosynthesis Inhibitor AKBA

AKBA (acetyl-11-keto-β-boswellic acid, 1 ) and KBA (11-keto-β-BA, 2 ) from Boswellia serrata Roxb. and Boswellia carterii Birdw. are direct, nonredox-type inhibitors of 5-lipoxygenase, the key enzyme for leukotriene biosynthesis (IC₅₀ = 1.5 and 3μM in intact neutrophils, respectively). In order to study the impact of the carboxyl function for enzyme inhibition, we synthesized novel analogues of boswellic acids. The C-4 alcohol derivative of KBA ( 4 ) still exerted 5-lipoxygenase inhibitory activity (IC₅₀ = 4.5 μM), whereas ( 8 ), the C-4 alcohol analogue of β-boswellic acid ( 7 ), the methyl ester analogue of KBA ( 5 ), and acetyl-11-keto-amyrin ( 9 ) possessed no inhibitory potential in concentrations up to 50 μM. These findings reveal that a hydrophilic group at C4 in combination with an 11-keto-function is essential for 5-lipoxygenase inhibition by boswellic acids.     

Two new triterpenoids from the resin of Boswellia carterii

Two new triterpenoids, 3-oxotirucalla-7,9(11),24-trien-21-oic acid (1) and 18Hα,3β,20β-ursanediol (2), along with 15 known triterpenes, α-amyrin, α-boswellic acid, β-boswellic acid, acetyl α-boswellic acid, acetyl β-boswellic acid, 9,11-dehydro-β-boswellic acid, 9,11-dehydro-α-boswellic acid, acetyl 11α-methoxy-β-boswellic acid, 11-keto-β-boswellic acid, acetyl 11-keto-β-boswellic acid, acetyl α-elemolic acid, 3β-hydroxytirucalla-8,24-dien-21-oic acid, elemonic acid, 3α-hydroxytirucalla-7,24-dien-21-oic acid, and 3α-hydroxytirucall-24-en-21-oic acid, were isolated from the resin of Boswellia carterii Birdw.     

Two new triterpenoids from the resin of Boswellia carterii

Two new triterpenoids, 3-oxotirucalla-7,9(11),24-trien-21-oic acid (1) and 18Hα,3β,20β-ursanediol (2), along with 15 known triterpenes, α-amyrin, α-boswellic acid, β-boswellic acid, acetyl α-boswellic acid, acetyl β-boswellic acid, 9,11-dehydro-β-boswellic acid, 9,11-dehydro-α-boswellic acid, acetyl 11α-methoxy-β-boswellic acid, 11-keto-β-boswellic acid, acetyl 11-keto-β-boswellic acid, acetyl α-elemolic acid, 3β-hydroxytirucalla-8,24-dien-21-oic acid, elemonic acid, 3α-hydroxytirucalla-7,24-dien-21-oic acid, and 3α-hydroxytirucall-24-en-21-oic acid, were isolated from the resin of Boswellia carterii Birdw.     

西黄丸中11-羰基-β-乙酰乳香酸的鉴别及含量测定

目的：建立西黄丸中11-羰基-β-乙酰乳香酸的定性定量检验方法.方法：采用薄层色谱法和高效液相色谱法建立西黄丸中乳香类成分11-羰基-β-乙酰乳香酸的方法.结果：运用建立的薄层色谱法检测12个生产厂家提供的17批西黄丸,均含有11-羰基-β-乙酰乳香酸,但含量差别大,运用高效液相色谱法对其进行含量测定,其中11-羰基-β-乙酰乳香酸含量最低为0.27％,最高为1.05％.结论：建立薄层色谱法和高效液相色谱法可用于西黄丸中11-羰基-β-乙酰乳香酸的定性定量检验,可作为西黄丸现行法定检验标准中乳香显微鉴别的有益补充.     

Studies on triterpenoid corticomimetics (III)

From olibanum, acetylboswellic acid (I) and boswellic acid (II) were isolated as mixed crystals of α-and β-forms in the ratio of 1 to 2 and 1 to 4, respectively. And acetyl-11-keto-β-boswellic acid (III) and 11-keto-β-boswellic acid (IV) were also isolated and their α-forms were not found in olibanum by GC/selected ion monitoring MS technique. Contents of four compounds were determined.     

HPLC法测定乳香药材中11-羰基-β-乙酰乳香酸的含量

目的测定乳香药材中11-羰基-β-乙酰乳香酸的含量,建立有效方法。方法采用HPLC法,二极管阵列检测器;Empower色谱工作站;用十八烷基硅烷键合硅胶为填充剂;C18柱(250×4.6mm,5μm);以乙腈-水-冰乙酸(79∶21∶0.1)为流动相;检测波长为249nm。结果11-羰基-β-乙酰乳香酸在12μg.mL-1~495μg.mL-1(r=0.9999)范围内线性关系良好,平均回收率为100.12%,RSD为1.51%(n=6)。结论所测11-羰基-β-乙酰乳香酸含量符合标准,本法可作为11-羰基-β-乙酰乳香酸的质量控制方法。     

腰痛宁胶囊中11-羰基-β-乙酰乳香酸的含量测定方法研究

目的建立腰痛宁胶囊中11-羰基-β-乙酰乳香酸的含量测定方法。方法采用高效液相色谱法测定腰痛宁胶囊中11-羰基-β-乙酰乳香酸的含量,色谱柱为Agilent SB-C 18(4.6×150mm,5μm),流动相为乙腈-0.1%甲酸(82∶18),检测波长为251nm,流速为1.0mL·min^-1,进样体积为10μL。结果11-羰基-β-乙酰乳香酸的线性范围:1.014~50.72μg·mL^-1(r=1),平均加样回收率为100.59%,RSD为0.88%(n=9)。结论所建立的方法准确、灵敏、简便,稳定性和重现性良好,专属性强,可较好地控制腰痛宁胶囊的质量。     

Discovery of cyclooxygenase inhibitors from medicinal plants used to treat inflammation

Eleven authenticated botanicals used in the traditional Chinese medicine Huo-Luo-Xiao-Ling Dan were screened for ligands to cyclooxygenase (COX) using pulsed ultrafiltration liquid chromatography–mass spectrometry, and a mass spectrometry-based enzyme assay was used to determine the concentration of each of 17 ligands that inhibited COX-1 or COX-2 by 50% (IC₅₀). Acetyl-11-keto-β-boswellic acid, β-boswellic acid, acetyl-α-boswellic acid, acetyl-β-boswellic acid, and betulinic acid were COX-1 selective inhibitors with IC₅₀ values of approximately 10 μM. Senkyunolide O and cryptotanshinone were COX-2 selective inhibitors with IC₅₀ values of 5 μM and 22 μM, respectively. Roburic acid and phenethyl-trans-ferulate inhibited COX-1 and COX-2 equally. COX inhibition and the IC₅₀ values of most of these natural product ligands have not been reported previously.     

西黄丸和活血止痛散中乳香及非法添加松香的薄层色谱鉴别

目的建立薄层色谱鉴别方法检测西黄丸和活血止痛散中的乳香药材及非法添加的松香。方法样品经甲醇超声提取,点样于硅胶GF254薄层板上,以甲苯-乙酸乙酯一庚烷一无水甲酸（8：2：1：0．3）为展开剂展开,先置紫外灯（254nm和366nm）下检视,再喷以茴香醛试液,并于105℃加热至条斑清晰,目光下再次检视。结果紫外光灯（254nm）及目光下,西黄丸和活血止痛散与乳香对照药材的薄层指纹图谱一致,使用对照品识别了11-羰基-β-乙酰乳香酸（AKBA）、11-羰基-β-乳香酸（KBA）、β-乳香酸（β-BA）和β-乙酰乳香酸（β-ABA）;紫外光灯（366nm）下,活血止痛散可见与当归对照药材一致的条斑。紫外光灯（254nm）下,某些西黄丸色谱中可见松香中松香酸的暗条斑。结论该法简便、专属,适用于西黄丸和活血止痛散薄层色谱鉴别和质量控制。     

Effect of food intake on the bioavailability of boswellic acids from a herbal preparation in healthy volunteers

In this study we investigated the effects of concomitant food intake on the bioavailability of distinct boswellic acids (BAs) from the test preparation BSE-018, a dry extract from Boswellia serrata gum resin. In a randomised, open, single-dose, two-way crossover study, healthy male subjects received three capsules of BSE-018 equivalent to 786 mg dry extract of Boswellia serrata gum resin either in the fasted state or together with a standardised high-fat meal. BA plasma concentrations were analysed for up to 60 h after oral dosing by reversed phase HPLC. As compared to the fasted state (treatment A), the administration of BSE-018 concomitantly with a high-fat meal (treatment B) led to several-fold increased areas under the plasma concentration-time curves as well as peak concentrations of beta-boswellic acid (betaBA), 11-keto-beta-boswellic acid (KbetaBA) and acetyl-11-keto-beta-boswellic acid (AKbetaBA). Plasma levels of both acetyl-alpha-boswellic acid (AalphaBA) and alphaBA became only detectable when administered with treatment B, i.e., the high-fat meal. Accordingly, pharmacokinetic data could be calculated for betaBA, KbetaBA and AKbetaBA (treatment A) and for betaBA, KbetaBA, AKbetaBA, alphaBA, and AalphaBA (treatment B). For the first time these data reveal detailed kinetics of BAs after oral dosing of an extract and demonstrate a profound effect of food intake on the pharmacokinetic profile of the BAs. This finding should be very important whenever BAs would be considered for therapeutic use.     

Modulation of Pgp function by boswellic acids

Boswellic acids, the main active ingredients of Boswellia serrata, are gaining more and more importance in the treatment of peritumoural oedema and chronic inflammatory diseases. They may be even considered as alternative drugs to corticosteroids in reducing cerebral peritumoural oedema. An important focus for drugs acting in the central nervous system is achieving a high extent of brain penetration. Today there is increasing evidence for the importance of transporters, especially P-glycoprotein (Pgp), for drug disposition and resulting clinical response. Pharmacokinetic studies revealed that the concentrations of the potent keto derivatives, the 11-keto-beta-boswellic acid (KBA) and the acetyl-11-keto-beta-boswellic acid (AKBA), in proportion to boswellic acids lacking a keto group, like the beta-boswellic acid, are much lower in plasma than in the orally administered extract. Moreover the brain/plasma ratio for KBA and AKBA determined in preliminary experiments on rats was only about 0.51 and 0.81, respectively, in spite of their lipophilicity. Until now little is known about the cerebral pharmacokinetics of boswellic acids and how it may be influenced. Since many drugs are known to interact with Pgp at the level of the intestine and the blood-brain barrier the modulatory potencies of the Boswellia serrata extract of H15(R) and the major boswellic acids on the transport activity of Pgp have been determined in two in vitro assays. A human lymphocytic leukaemia cell line (VLB cells) expressing Pgp was chosen as model for human Pgp, and porcine brain capillary endothelial cells (PBCEC cells) were taken as model for the blood-brain barrier using calcein acetoxymethyl ester (calcein-AM) as Pgp substrate. It was found that the Boswellia extract, as well as the keto-boswellic acids inhibit the transport activity of Pgp in the micromolecular range in both cell types. No modulation was observed using those boswellic acids which have no keto group in their structure. The inhibition of Pgp at the blood-brain barrier by Boswellia extract is probably not relevant for the brain availability of other Pgp substrates, because of the low plasma levels determined for KBA and AKBA. However the presented data could not exclude the possibility of drug interactions caused by modulation of Pgp by extracts of Boswellia serrata on the gastrointestinal level.     

Effects of gum resin of Boswellia serrata in patients with chronic colitis

Patients studied here suffered from chronic colitis characterized by vague lower abdominal pain, bleeding per rectum with diarrhoea and palpable tender descending and sigmoid colon. The inflammatory process in colitis is associated with increased formation of leukotrienes causing chemotaxis, chemokinesis, synthesis of superoxide radicals and release of lysosomal enzymes by phagocytes. The key enzyme for leukotriene biosynthesis is 5-lipoxygenase. Boswellic acids were found to be non-redox, non-competitive specific inhibitors of the enzyme 5-lipoxygenase. We studied the gum resin of Boswellia serrata for the treatment of this disease. Thirty patients, 17 males and 13 females in the age range of 18 to 48 years with chronic colitis were included in this study. Twenty patients were given a preparation of the gum resin of Boswellia serrata (900 mg daily divided in three doses for 6 weeks) and ten patients were given sulfasalazine (3 gm daily divided in three doses for 6 weeks) and served as controls. Out of 20 patients treated with Boswellia gum resin 18 patients showed an improvement in one or more of the parameters: including stool properties, histopathology as well as scanning electron microscopy, besides haemoglobin, serum iron, calcium, phosphorus, proteins, total leukocytes and eosinophils. In the control group 6 out of 10 patients showed similar results with the same parameters. Out of 20 patients treated with Boswellia gum resin 14 went into remission while in case of sulfasalazine remission rate was 4 out of 10. In conclusion, this study shows that a gum resin preparation from Boswellia serrata could be effective in the treatment of chronic colitis with minimal side effects.     

3-乙酰基-11-酮-β-乳香酸的抗炎作斥及其衍生物的化学修饰

乳香酸（Bas）是乳香提取物中的活性成分,乳香酸在治疗炎症方面的疾病如类风湿关节炎、慢性支气管炎、哮喘以及慢性发炎性肠道疾病（溃疡性结肠炎和克罗恩病）已经显示出显著的药理活性。数据表明,3-乙酰基-11-酮-β-乳香酸（AKBA）被认为在各种乳香酸中是最强大的。AKBA被发现和确认为5-脂肪氧合酶（5-LOX）强大的抑制剂;AKBA的其他药理活性研究发现,它还充当了p38-MAP激酶强大的抑制剂。为了得到更多的AKBA,它的衍生物BA、KBA、ABA经过一系列化学修饰乙酰化和烯丙基氧化转化为AKBA,从而AKBA的量根据乳香树种和相应树脂质量从0．1％～3．0％上升到25％～35％。     

Comparison of the irritation potentials of Boswellia serrata gum resin and of acetyl-11-keto-beta-boswellic acid by in vitro cytotoxicity tests on human skin-derived cell lines

Indian frankincense is a gum resin from Boswellia serrata of Burseraceae used in Ayurveda and Western medicine for the antinflammatory effects of boswellic acids, particularly 3-O-acetyl-11-keto-beta-boswellic acid (AKBA). We evaluated in vitro cytotoxicities of B. serrata extract and AKBA on differentiated and undifferentiated keratinocytes (HaCaT and NCTC 2544), and foetal dermal fibroblasts (HFFF2), using neutral red uptake (NRU), MTT, and DNA assays. Comparison between NRU and MTT, and between the extract and AKBA, suggested a relatively higher toxicity of both substances on lysosomes respect to mitochondria. Extract cytotoxicity on lysosomes was higher in NCTC and HFFF2 than on the more differentiated HaCaT. DNA assay showed low extract inhibition on HFFF2 proliferation, possibly due to lower growth rate, and a stronger effect on NCTC than on HaCaT, possibly related to higher proapoptotic effect on the less differentiated NCTC, as also suggested by higher AKBA toxicity on NCTC than on HaCaT. In general, gum resin and AKBA toxicities were slightly lower or higher than that of the reference compound SDS. Our in vitro model allowed to compare the sensitivities of different human skin cells to B. serrata, and indicated that the gum resin and AKBA exert moderate to low toxicity on the skin.     

Concentration-dependent potentiating and inhibitory effects of Boswellia extracts on 5-lipoxygenase product formation in stimulated PMNL

Preparations from the gum of Boswellia spec. have been used in the traditional medicine for the treatment of inflammatory diseases. Extracts from B. serrata gum were shown to inhibit leukotriene biosynthesis by impairing the 5-lipoxygenase (5-LO) activity. In order to identify the minimal effective concentrations of extracts in vitro we studied the effects of ethanolic extracts from commercially available resins from two regions (B. serrata gum from India and Olibanum in granis from Arabia) on the 5-LO product formation from endogenous substrate in calcium and ionophore stimulated neutrophils in a defined concentration range. Both extracts inhibited 5-LO product formation in vitro in concentrations greater than 10 to 15 micrograms/ml as reported previously for an ethanolic B. serrata extract. In contrast, lower concentrations of extracts (1 to 10 micrograms/ml) even potentiated 5-LO product formation, especially the biosynthesis of 5(S)-HETE. The in vitro data underline the major importance of drug standardization when Boswellia resin containing preparations are used for the treatment of diseases.     

A reversed phase high performance liquid chromatography method for the analysis of boswellic acids in Boswellia serrata.

An HPLC method for the separation of boswellic acids, the active constituents in Boswellia serrata resin has been developed. The first accurate determination of 6 individual acids was possible in the resin as well as in multi-component preparations. By using an acidic mobile phase, raised temperature and a 4 microm Synergi MAX-RP 80 A column the acids could be detected at levels as low as 0.9 microg/ml. The study of market products revealed significant variations in the content of these pharmacologically active compounds in commercial samples.     

乳香的化学成分

目的研究乳香的化学成分。方法应用色谱技术进行分离和纯化,IR,NMR,MS等波谱解析化学结构。结果从乳香中分离出6个化合物,分别鉴定为α-乙酰乳香酸(1),β-乙酰乳香酸(2),羽扇-20(29)-烯-3α-乙酰氧基-24-酸(3),α-乳香酸(4),β-乳香酸(5),11-羰基-β-乙酰乳香酸(6)。结论化合物3为新成分。     

Transdermal microemulsions of Boswellia carterii Bird: formulation,characterization and in vivo evaluation of anti-inflammatory activity

Abstract

Context: Boswellia species are trees (family: Bruseraceae) found in India, Northern Africa and the Middle East.

Objective: This study aims at formulating low dose biologically active fraction from the oleogum resin of Boswellia carterii (BC) in transdermal (TD) microemulsions (MEs) to acquire promoted anti-inflammatory efficacy.

Materials and methods: The bioactive fraction of the oleogum resin of BC was tested for solubility in different components. The most efficient were selected for constructing phase diagrams for ME preparation. The bioactive fraction was assayed by high performance liquid chromatography for 3-acetyl–11-keto-β-boswellic acid (AKBA), at 210?nm. The bioactive fraction was incorporated in 6?MEs. ME systems were evaluated for drug content and optimized systems were tested for characterization, permeation, skin irritancy and in vivo evaluation of anti-inflammatory activity.

Results and Discussion: Two systems were selected; ME1 and ME4 composed of Tween 80: PEG 400 at 1:1 and 2:1 ratio, with oil content 7.78 and 17.5%, respectively. The systems showed high encapsulation efficiency >83%, small droplet size <100?nm, and suitable pH for topical application. Permeation parameters for ME1 were higher compared to ME4. Both MEs were non irritant. ME1 showed significantly higher anti-inflammatory activity versus the standard TD anti-inflammatory piroxicam.

Conclusions: Optimized TD BC MEs could be used as a safe, effective and long acting alternative to oral anti-inflammatories, providing higher and prolonged efficacy and better patient compliance.     

乳香、制乳香含量测定研究

目的建立HPLC法测定乳香及制乳香中11-羰基-β-乙酰乳香酸的含量。方法采用Agilent TC-C18柱,流动相为乙腈-0.1%冰醋酸溶液（80∶20）,流速为1.0mL.min-1,检测波长为250nm,柱温为30℃。结果 11-羰基-β-乙酰乳香酸在0.1535～2.4560μg范围内线性良好,r=0.99999。平均回收率为97.62%,RSD=1.36%。结论本法专属、快速、准确,可用于乳香的含量测定。