Boswellic acids: privileged structures to develop lead compounds for anticancer drug discovery

Therapeutic potential of boswellic acids: an update patent review (2016-2023)

INTRODUCTION

Boswellic acids (BAs) are a group of pentacyclic triterpenoids of the ursane and oleanane type. They have shown very interesting biological properties that have led to the development of a number of synthesis protocols. Both natural BAs and their synthetic derivatives may be useful in the treatment of a variety of cancers, viral infections and inflammatory diseases.

AREAS COVERED

This review covers patents relating to the therapeutic activities of natural BAs and their synthetic derivatives. The latest patented studies of boswellic acids (are summarized by using the keywords 'boswellic acid,' in SciFinder, PubMed, and Google Patents and databases in the year from 2016 to 2023.

EXPERT OPINION

Boswellic acids have shown potent antiviral, anticancer and anti-inflammatory potential. Few BAs analogues have been prepared by modification at the C24-CO2H functional groups. In particular, the C-24 amide and amino analogues have shown enhanced anticancer effects compared to the parent AKBA. In addition, BAs have the ability to form conjugates with other antiviral, anti-inflammatory and anticancer drugs that synergistically enhance their biological efficacy. In addition, this conjugation strategy will increase the solubility and bioavailability of BAs, which is one of the most important issues in the development of BAs.

Advances and Challenges in the Analysis of Boswellic Acids by Separation Methods

Boswellia resin is an exudate from the cut bark of Boswellia trees. The main constituents of pharmacological interest are boswellic acids (pentacyclic triterpenoids), namely α-boswellic acid, β-boswellic acid, 3-O-acetyl-α-boswellic acid, 3-O-acetyl-β-boswellic acid, 11-keto-β-boswellic acid, and 3-O-acetyl-11-keto-β-boswellic acid. Nowadays, dietary supplements with Boswellia serrata extract are used in the treatment of inflammatory joint diseases. Additionally, the constituents of Boswellia resin have shown potential for the treatment of other chronic inflammatory diseases and various types of cancer. Separation methods including ultra/high-performance liquid chromatography, gas chromatography, thin layer chromatography, supercritical fluid chromatography, and capillary electrochromatography coupled with UV or MS detection have been used for the determination of boswellic acids in various matrices (mostly plant material and biological samples). This review aims to provide a comprehensive summary of these separation methods, offering a critical discussion of their strengths and limitations in the analysis of boswellic acids. The knowledge of various separation methods plays a pivotal role in the quality control of herbal dietary supplements and the monitoring of the metabolism and pharmacokinetics of their constituents. The approaches based on metabolomics and network pharmacology represent new ways of fingerprinting secondary metabolites in Boswellia resin increasing the comprehensiveness of the output of these methods resulting in safer dietary supplements.

Anti-cancer properties of boswellic acids: mechanism of action as anti-cancerous agent

With the advent of highly effective plant-based medications with few or no side effects, the use of phytomedicines against complex diseases such as cancer is becoming more widespread. The broadly recognized pentacyclic triterpenes known as boswellic acids (BAs) are derived from the oleogum resin, or frankincense, extracted from the plant species of the genus Boswellia. The frankincense mixture contains various BA types, each having a different potential and helping treat certain cancers. This review focuses on details regarding the traits of the BAs, their roles as anti-cancer agents, the mechanism underlying their activities, and the function of their semi-synthetic derivatives in managing and treating certain cancers. The review also explores the biological sources of BAs, how they are conserved, and how biotechnology might help preserve and improve in vitro BA production. The review concludes that the BAs and their semi-synthetic derivatives are effective against a broad spectrum of cancer cell lines. The detailed information in the review can be helpful for researchers to gain more information about BAs and BA-based medications for efficient and cost-effective cancer treatments.

Unusually cyclized triterpenoids: occurrence, biosynthesis and chemical synthesis

Covering: 2009 to 2021Biosynthetically, most of the syntheses of triterpenes follow the cascade cyclization and rearrangement of the acyclic precursors viz., squalene (S) and 2,3-oxidosqualene (OS), which lead to the very well known tetra- and pentacyclic triterpene skeletons. Aside from these, numerous other triterpenoid molecules are also reported from various natural sources and their structures are derived from "S" and "OS" via some unusual cyclization operations which are different from the usual tetra- and pentacyclic frameworks. Numerous compelling advances have been made and reported in the identification of these unusual cyclized mono-, di-, tri- and tetracyclic triterpenes between 2009 and 2021. Besides a dramatic increase in the newly isolated uncommon cyclized triterpenoids, substantial progress in the (bio)-synthesis of these triterpenes has been published along with significant progress in their biological effects. In this review, 180 new unusual cyclized triterpenoids together with their demonstrated biogenetic pathways, syntheses and biological effects will be categorized and discussed.

Discovery of New Boswellic Acid Hybrid 1H-1,2,3-Triazoles for Diabetic Management: In Vitro and In Silico Studies

A series of 24 new 1H-1,2,3-triazole hybrids of 3-O-acetyl-11-keto-β-boswellic acid (β-AKBA (1)) and 11-keto-β-boswellic acid (β-KBA (2)) was designed and synthesized by employing "click" chemistry in a highly efficient manner. The 1,3-dipolar cycloaddition reaction between β-AKBA-propargyl ester intermediate 3 or β-KBA-propargyl ester intermediate 4 with substituted aromatic azides 5a-5k in the presence of copper iodide (CuI) and Hünig's base furnished the desired products-1H-1,2,3-triazole hybrids of β-AKBA (6a-6k) and β-KBA (7a-7k)-in high yields. All new synthesized compounds were characterized by ¹H-, ¹³C-NMR spectroscopy, and HR-ESI-MS spectrometry. Furthermore, their α-glucosidase-inhibitory activity was evaluated in vitro. Interestingly, the results obtained from the α-glucosidase-inhibitory assay revealed that all the synthesized derivatives are highly potent inhibitors, with IC₅₀ values ranging from 0.22 to 5.32 µM. Among all the compounds, 6f, 7h, 6j, 6h, 6g, 6c, 6k, 7g, and 7k exhibited exceptional inhibitory potency and were found to be several times more potent than the parent compounds 1 and 2, as well as standard acarbose. Kinetic studies of compounds 6g and 7h exhibited competitive and mixed types of inhibition, with ki values of 0.84 ± 0.007 and 1.18 ± 0.0012 µM, respectively. Molecular docking was carried out to investigate the binding modes of these compounds with α-glucosidase. The molecular docking interactions indicated that that all compounds are well fitted in the active site of α-glucosidase, where His280, Gln279, Asp215, His351, Arg442, and Arg315 mainly stabilize the binding of these compounds. The current study demonstrates the usefulness of incorporating a 1H-1,2,3-triazole moiety into the medicinally fascinating boswellic acids skeleton.

Analysis of the pharmacodynamic difference between Xiaojin Pills taken with Chinese Baijiu and water based on serum pharmacochemistry and pharmacokinetics

ETHNOPHARMACOLOGICAL RELEVANCE

Xiaojin Pills (XJPs), which has the function of dissipating knots and dispersing swelling, removing blood stasis, and relieving pain, is a classic prescription for the treatment of mammary glands hyperplasia. It is also the first choice of Chinese patent medicine for the clinical treatment of mammary glands hyperplasia in contemporary traditional Chinese medicine clinics. Previous studies have shown that the efficacy of XJPs "taken orally after soaked with Chinese Baijiu" in tradition was significantly better than that of taking it orally with water in modern in terms of activating the blood, anti-inflammation, analgesia, anti-mammary gland hyperplasia, anti-breast cancer and its metastasis in vitro and in vivo, especially under low-dose conditions. However, the material basis for the difference in efficacy between XJP&B and XJP&W is still unclear.

AIM OF THE STUDY

To analyze the material basis of the significant difference in efficacy between XJP&B and XJP&W from the perspective of serum pharmacochemistry and pharmacokinetics, and clarified the scientific connotation of XJPs "taken orally after soaked with Chinese Baijiu".

MATERIALS AND METHODS

Ultra-high performance liquid chromatography-mass spectrometry combined with a multivariate statistical analysis method were used to screen the differential components in the Chinese Baijiu extract and the water extract of XJPs and the corresponding residues, so as to clarify the differential components between XJP&B and XJP&W in vitro. The migrating components in the blood after XJP&B and XJP&W were characterized by serum pharmacochemical methods, in order to clarify the differential components in rats. The pharmacokinetic parameters of the representative components absorbed into the blood were compared between XJP&B and XJP&W by the pharmacokinetics study method, in order to determine the dynamic changes of the representative components in rats.

RESULTS

The identification results of different components in vitro showed that there were 34 and 12 different compounds between the Chinese Baijiu extract and water extract of XJPs, and the residues after Chinese Baijiu extraction and water extraction, respectively. The content of different components such as arachidonic acid, ursolic acid, 3-acetyl-11-keto-β-boswellic acid, 2α-hydroxyursolic acid, and oleanolic acid was higher in the Chinese Baijiu extract, which was more than twice the content in the water extract. The results of the serum pharmacochemistry study indicated that 42 prototype components were identified in the serum of rats after XJP&B and XJP&W, including organic acids, alkaloids, steroids, and terpenoids. And XJP&B increased the absorption of the prototype components of organic acids in XJPs into the blood. The pharmacokinetic study results of representative components demonstrated that the mean plasma concentration-time profile and pharmacokinetic parameters of muscone, aconitine, and 3-acetyl-11-keto-β-boswellic acid were significantly different between XJP&B and XJP&W. Compared with XJP&W, the C_max and AUC_0-t of muscone and aconitine in XJP&B were higher, and the T_1/2 and MRT_0-t of 3-acetyl-11-keto-β-boswellic acid in XJP&B were relatively longer.

CONCLUSION

This research proved that "taking XJPs orally after being soaked with Chinese Baijiu" can increase the dissolution and absorption of active ingredients in XJPs, increase the plasma concentration and content of representative ingredients, and prolong its action time, thus enhancing the biological activity of XJPs in vitro and in vivo. To a certain extent, this study revealed the material basis of the significantly better efficacy of XJP&B than XJP&W and clarified the scientific connotation of XJPs "taken orally after soaked with Chinese Baijiu", which can provide a theoretical basis for the optimization of XJPs' clinical administration method.

Recent Advances Regarding the Molecular Mechanisms of Triterpenic Acids: A Review (Part II)

Triterpenic acids are a widespread class of phytocompounds which have been found to possess valuable therapeutic properties such as anticancer, anti-inflammatory, hepatoprotective, cardioprotective, antidiabetic, neuroprotective, lipolytic, antiviral, and antiparasitic effects. They are a subclass of triterpenes bearing a characteristic lipophilic structure that imprints unfavorable in vivo properties which subsequently limit their applications. The early investigation of the mechanism of action (MOA) of a drug candidate can provide valuable information regarding the possible side effects and drug interactions that may occur after administration. The current paper aimed to summarize the most recent (last 5 years) studies regarding the MOA of betulinic acid, boswellic acid, glycyrrhetinic acid, madecassic acid, moronic acid, and pomolic acid in order to provide scientists with updated and accessible material on the topic that could contribute to the development of future studies; the paper stands as the sequel of our previously published paper regarding the MOA of triterpenic acids with therapeutic value. The recent literature published on the topic has highlighted the role of triterpenic acids in several signaling pathways including PI3/AKT/mTOR, TNF-alpha/NF-kappa B, JNK-p38, HIF-α/AMPK, and Grb2/Sos/Ras/MAPK, which trigger their various biological activities.

How Should the Worldwide Knowledge of Traditional Cancer Healing Be Integrated with Herbs and Mushrooms into Modern Molecular Pharmacology?

Traditional herbal medicine (THM) is a “core” from which modern medicine has evolved over time. Besides this, one third of people worldwide have no access to modern medicine and rely only on traditional medicine. To date, drugs of plant origin, or their derivates (paclitaxel, vinblastine, vincristine, vinorelbine, etoposide, camptothecin, topotecan, irinotecan, and omacetaxine), are very important in the therapy of malignancies and they are included in most chemotherapeutic regimes. To date, 391,000 plant and 14,000 mushroom species exist. Their medical and biochemical capabilities have not been studied in detail. In this review, we systematized the information about plants and mushrooms, as well as their active compounds with antitumor properties. Plants and mushrooms are divided based on the regions where they are used in ethnomedicine to treat malignancies. The majority of their active compounds with antineoplastic properties and mechanisms of action are described. Furthermore, on the basis of the available information, we divided them into two priority groups for research and for their potential of use in antitumor therapy. As there are many prerequisites and some examples how THM helps and strengthens modern medicine, finally, we discuss the positive points of THM and the management required to transform and integrate THM into the modern medicine practice.

Frankincense diterpenes as a bio-source for drug discovery

INTRODUCTION

Frankincense (Boswellia sp.) gum resins have been employed as an incense in cultural and religious ceremonies for many years. Frankincense resin has over the years been employed to treat depression, inflammation, and cancer in traditional medicines.

AREAS COVERED

This inclusive review focuses on the significance of frankincense diterpenoids, and in particular, incensole derivatives for establishment future treatments of depression, neurological disorders, and cancer. The authors survey the available literature and furnish an overview of future perspectives of these intriguing molecules.

EXPERT OPINION

Numerous diterpenoids including cembrane, prenylaromadendrane, and the verticillane-type have been isolated from various Boswellia resins. Cembrane-type diterpenoids occupy a crucial position in pharmaceutical chemistry and related industries because of their intriguing biological and encouraging pharmacological potentials. Several cembranes have been reported to possess anti-Alzheimer, anti-inflammatory, hepatoprotective, and antimalarial effects along with a good possibility to treat anxiety and depression. Although some slight drawbacks of these compounds have been noted, including the selectivity of these diterpenoids, there is a great need to address these in future research endeavors. Moreover, it is vitally important for medicinal chemists to prepare libraries of incensole-heterocyclic analogs as well as hybrid compounds between incensole or its acetate and anti-depressant or anti-inflammatory drugs.

Validation of the Antioxidant and Enzyme Inhibitory Potential of Selected Triterpenes Using In Vitro and In Silico Studies, and the Evaluation of Their ADMET Properties

The antioxidant and enzyme inhibitory potential of fifteen cycloartane-type triterpenes’ potentials were investigated using different assays. In the phosphomolybdenum method, cycloalpioside D (6) (4.05 mmol TEs/g) showed the highest activity. In 1,1-diphenyl-2-picrylhydrazyl (DPPH*) radical and 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) cation radical scavenging assays, cycloorbicoside A-7-monoacetate (2) (5.03 mg TE/g) and cycloorbicoside B (10) (10.60 mg TE/g) displayed the highest activities, respectively. Oleanolic acid (14) (51.45 mg TE/g) and 3-O-β-d-xylopyranoside-(23R,24S)-16β,23;16α,24-diepoxycycloart-25(26)-en-3β,7β-diol 7-monoacetate (4) (13.25 mg TE/g) revealed the highest reducing power in cupric ion-reducing activity (CUPRAC) and ferric-reducing antioxidant power (FRAP) assays, respectively. In metal-chelating activity on ferrous ions, compound 2 displayed the highest activity estimated by 41.00 mg EDTAE/g (EDTA equivalents/g). The tested triterpenes showed promising AChE and BChE inhibitory potential with 3-O-β-d-xylopyranoside-(23R,24S)-16β,23;16α,24-diepoxycycloart-25(26)-en-3β,7β-diol 2′,3′,4′,7-tetraacetate (3), exhibiting the highest inhibitory activity as estimated from 5.64 and 5.19 mg GALAE/g (galantamine equivalent/g), respectively. Compound 2 displayed the most potent tyrosinase inhibitory activity (113.24 mg KAE/g (mg kojic acid equivalent/g)). Regarding α-amylase and α-glucosidase inhibition, 3-O-β-d-xylopyranoside-(23R,24S)-16β,23;16α,24-diepoxycycloart-25(26)-en-3β,7β-diol (5) (0.55 mmol ACAE/g) and compound 3 (25.18 mmol ACAE/g) exerted the highest activities, respectively. In silico studies focused on compounds 2, 6, and 7 as inhibitors of tyrosinase revealed that compound 2 displayed a good ranking score (−7.069 kcal/mole) and also that the ΔG free-binding energy was the highest among the three selected compounds. From the ADMET/TOPKAT prediction, it can be concluded that compounds 4 and 5 displayed the best pharmacokinetic and pharmacodynamic behavior, with considerable activity in most of the examined assays.

A strategy to discover lead chemome from traditional Chinese medicines based on natural chromatogram-effect correlation (NCEC) and natural structure-effect correlation (NSEC): Mahonia bealei and Mahonia fortunei as a case study

Lead compound is an important concept for modern drug discovery. In this study, a new concept of lead chemome and an efficient strategy to discover lead chemome were proposed. Compared with the concept of lead compound, lead chemome can provide not only the starting point for drug development, but also the direction for structure optimization. Two traditional Chinese medicines of Mahonia bealei and Mahonia fortunei were used as examples to illustrate the strategy. Based on natural chromatogram-effect correlation (NCEC), berberine, palmatine and jatrorrhizine were discovered as acetylcholinesterase (AchE) inhibitors. Taking the three compounds as template molecules, a lead chemome consisting of 10 structurally related natural compounds were generated through natural structure-effect correlation (NSEC). In the lead chemome, the IC₅₀ values of jatrorrhizine, berberine, coptisine, palmatine and epiberberine are at nanomolar level, which are comparable to a widely used drug of galantamine. Pharmacophore modeling shows that the positive ionizable group and aromatic rings are important substructures for AchE inhibition. Molecular docking further shows that pi-cation interaction and pi-pi stacking are critical for compounds to maintain nanomolar IC₅₀ values. The structure-activity information is helpful for drug design and structure optimization. This work also expanded the traditional understanding of "stem is the medicinal part of Mahonia bealei and Mahonia fortunei". Actually, all parts except the leaf of Mahonia bealei exhibited potent AchE-inhibitory activity. This study provides not only a strategy to discover lead chemome for modern drug development, but also a reference for the application of different parts of medicinal plants.