3-O-acetyl-11-keto-boswellic acid decreases basal intracellular Ca2+ levels and inhibits agonist-induced Ca2+ mobilization and mitogen-activated protein kinase activation in human monocytic cells

Synthesis of 3-O-Acetyl-11-keto-β-boswellic Acid (AKBA)-Derived Amides and Their Mitochondria-Targeted Antitumor Activities

In this study, we synthesized a series of amide and mitochondria-targeted derivatives with 3-O-acetyl-11-keto-β-boswellic acid (AKBA) as the parent structure and an ethylenediamine moiety as the link chain. Compound 5e, a mitochondrial-targeting potential derivative, showed significantly stronger antitumor activity than that of AKBA, and it could induce vacuolization of A549 cells and stimulate the production of reactive oxygen species (ROS) in a time- and concentration-dependent manner. The antioxidant N-acetylcysteine (NAC) could inhibit the ROS level but could not suppress vacuolization and cell death induced by 5e. Further studies demonstrated that 5e caused abnormal opening of mitochondrial permeability transition pore (MPTP) and a decrease of mitochondrial membrane potential; additionally, it caused cell cycle arrest in G₀/G₁ but did not induce apoptosis. 5e represented a compound with improved antiproliferative effects for cancer therapy working through new mechanisms.

Molecular evidences on anti-inflammatory, anticancer, and memory-boosting effects of frankincense

Chemical diversity of natural products with drug-like features has attracted much attention from medicine to develop more safe and effective drugs. Their anti-inflammatory, antitumor, analgesic, and other therapeutic properties are sometimes more successful than chemical drugs in controlling disease due to fewer drug resistance and side effects and being more tolerable in a long time. Frankincense, the oleo gum resin extracted from the Boswellia species, contains some of these chemicals. The anti-inflammatory effect of its main ingredient, boswellic acid, has been traditionally used to treat many diseases, mainly those target memory functions. In this review, we have accumulated research evidence from the beneficial effect of Frankincense consumption in memory improvement and the prevention of inflammation and cancer. Besides, we have discussed the molecular pathways mediating the therapeutic effects of this natural supplement.

Plant Secondary Metabolites: An Opportunity for Circular Economy

Moving toward a more sustainable development, a pivotal role is played by circular economy and a smarter waste management. Industrial wastes from plants offer a wide spectrum of possibilities for their valorization, still being enriched in high added-value molecules, such as secondary metabolites (SMs). The current review provides an overview of the most common SM classes (chemical structures, classification, biological activities) present in different plant waste/by-products and their potential use in various fields. A bibliographic survey was carried out, taking into account 99 research articles (from 2006 to 2020), summarizing all the information about waste type, its plant source, industrial sector of provenience, contained SMs, reported bioactivities, and proposals for its valorization. This survey highlighted that a great deal of the current publications are focused on the exploitation of plant wastes in human healthcare and food (including cosmetic, pharmaceutical, nutraceutical and food additives). However, as summarized in this review, plant SMs also possess an enormous potential for further uses. Accordingly, an increasing number of investigations on neglected plant matrices and their use in areas such as veterinary science or agriculture are expected, considering also the need to implement "greener" practices in the latter sector.

Acetyl-11-keto-β-boswellic acid prevents testicular torsion/detorsion injury in rats by modulating 5-LOX/LTB4 and p38-MAPK/JNK/Bax/Caspase-3 pathways

AIMS

Testicular torsion/detorsion (T/D) is a critical medical condition that necessitates prompt surgical intervention to avoid testicular atrophy and infertility. The use of natural compounds may protect against the associated detrimental oxidative stress and inflammatory responses. Interestingly, acetyl-11-keto-β-boswellic acid (AKBA), the main active constituent of Boswellia resin, has shown potent inhibitory effect on 5-lipoxygenase enzyme which converts arachidonic acid into inflammatory mediators. Therefore, this study was conducted to assess the protective mechanisms by which AKBA may protect against testicular T/D injury in rats.

MAIN METHODS

Male rats were randomly distributed into five groups: Sham, AKBA (50 mg/kg, p.o.), unilateral testicular T/D, AKBA at two dose levels (25 or 50 mg/kg for 15 successive days) followed by T/D. Histological examination and Johnsen's score were performed to assess testicular injury and perturbations in spermatogenesis. Biochemical parameters included markers of testicular function (serum testosterone), oxidant/antioxidant status (malondialdehyde, glutathione), inflammation (5-lipoxygenase, leukotriene-B4, myeloperoxidase, interleukin-1β, interleukin-6), apoptosis (Bax, Bcl2, caspase-3), DNA integrity (quantitative DNA fragmentation, DNA laddering, PARP-1), energy production (ATP), in addition to p38 MAPK and JNK protein expression.

KEY FINDINGS

In a dose dependent manner, AKBA significantly inhibited testicular T/D-induced upregulation of 5-LOX/LTB4 and p38-MAPK/JNK/Bax pathways and their associated downstream inflammatory and apoptotic cascades. These effects were accompanied with ATP replenishment and DNA preservation, resulting ultimately in salvage of the testis.

SIGNIFICANCE

Unprecedentedly, the present mechanistic study revealed the pathways by which AKBA may inhibit testicular T/D injury and offered a novel protective approach that may attenuate the severity of this condition.

Plant terpenes: defense responses, phylogenetic analysis, regulation and clinical applications

The terpenoids constitute the largest class of natural products and many interesting products are extensively applied in the industrial sector as flavors, fragrances, spices and are also used in perfumery and cosmetics. Many terpenoids have biological activities and also used for medical purposes. In higher plants, the conventional acetate-mevalonic acid pathway operates mainly in the cytosol and mitochondria and synthesizes sterols, sesquiterpenes and ubiquinones mainly. In the plastid, the non-mevalonic acid pathway takes place and synthesizes hemi-, mono-, sesqui-, and diterpenes along with carotenoids and phytol tail of chlorophyll. In this review paper, recent developments in the biosynthesis of terpenoids, indepth description of terpene synthases and their phylogenetic analysis, regulation of terpene biosynthesis as well as updates of terpenes which have entered in the clinical studies are reviewed thoroughly.

Interference of boswellic acids with the ligand binding domain of the glucocorticoid receptor

Boswellic acids (BAs) possess anti-inflammatory properties in various biological models with similar features to those of glucocorticoids (GCs), such as suppression of the release of pro-inflammatory cytokines. Hence, the molecular mechanism of BAs responsible for their anti-inflammatory features might be attributable to interference with the human glucocorticoid receptor (GR). Due to obvious structural similarities with GCs, we conducted pharmacophore studies as well as molecular docking simulations of BAs as putative ligands at the ligand binding site (LBS) of the GR in distinct functional states. In order to verify receptor binding and functional activation of the GR by BAs, radiometric binding assays as well as GR response element-dependent luciferase reporter assay were performed with dexamethasone (DEX) as a functional positive control. With respect to the observed position of GCs in GR crystal complexes in the active antagonist state, BAs docked in a flipped orientation with estimated binding constants reflecting nanomolar affinities. For validation, DEX and other steroids were successfully redocked into their crystal poses in similar ranges as reported in the literature. In line with the pharmacophore and docking models, the BAs were strong GR binders (radiometric binding assay), albeit none of the BAs activated the GR in the reporter gene assay, when compared to the GC agonist DEX. The flipped scaffolds of all BAs dislodge the known C-11 function from its receiving amino acid (Asn564), which may explain the silencing effects of receptor-bound BAs in the reporter gene assay. Together, our results constitute a compelling example of rigid keys acting in an adaptable lock qualifying as a reversed induced fit mechanism, thereby extending the hitherto published knowledge about molecular target interactions of BAs.

Boswellic acids reduce Th17 differentiation via blockade of IL-1β-mediated IRAK1 signaling

Interferon-gamma producing CD4(+) T (Th1) cells and IL-17-producing CD4(+) T (Th17) cells are involved in the pathogenesis of several autoimmune diseases including multiple sclerosis. Therefore, the development of treatment strategies controlling the generation and expansion of these effector cells is of high interest. Frankincense, the resin from trees of the genus Boswellia, and particularly its prominent bioactive compound acetyl-11-keto-β-boswellic acid (AKBA), have potent anti-inflammatory properties. Here, we demonstrate that AKBA is able to reduce the differentiation of human CD4(+) T cells to Th17 cells, while slightly increasing Th2- and Treg-cell differentiation. Furthermore, AKBA reduces the IL-1β-triggered IL-17A release of memory Th17 cells. AKBA may affect IL-1β signaling by preventing IL-1 receptor-associated kinase 1 phosphorylation and subsequently decreasing STAT3 phosphorylation at Ser727, which is required for Th17-cell differentiation. The effects of AKBA on Th17 differentiation and IL-17A release make the compound a good candidate for potential treatment of Th17-driven diseases.

Evaluation of the efficacy of ginger, Arabic gum, and Boswellia in acute and chronic renal failure

This study was conducted to evaluate the effects of Zingiber officinale Roscoe (Ginger), Arabic gum (AG), and Boswellia on both acute and chronic renal failure (CRF) and the mechanisms underlying their effects. Acute renal failure was induced by 30 min ischemia followed by 24 h reperfusion, while CRF was induced by adenine feeding for 8 weeks. Prophylactic oral administration of ginger, AG, Boswellia, or vehicle (in control groups) was started 3 days before and along with adenine feeding in different groups or 7 days before ischemia-reperfusion. Ginger and AG showed renoprotective effects in both models of renal failure. These protective effects may be attributed at least in part to their anti-inflammatory properties as evident by attenuating serum C-reactive protein levels and antioxidant effects as evident by attenuating lipid peroxidation marker, malondialdehyde levels, and increasing renal superoxide dismutase activity. Ginger was more potent than AG in both models of renal failure. However, Boswellia showed only partial protective effect against both acute renal failure and CRF and it had no antioxidant effects. Finally, we can say that ginger and AG could be beneficial adjuvant therapy in patients with acute renal failure and CRF to prevent disease progression and delay the need for renal replacement therapy.

Boswellic acids from frankincense inhibit lipopolysaccharide functionality through direct molecular interference

Lipophilic extracts of gum resins of Boswellia species (BSE) are used in folk medicine to treat various inflammatory disorders and infections. The molecular background of the beneficial pharmacological effects of such extracts is still unclear. Various boswellic acids (BAs) have been identified as abundant bioactive ingredients of BSE. Here we report the identification of defined BAs as direct inhibitors of lipopolysaccharide (LPS) functionality and LPS-induced cellular responses. In pull-down experiments, LPS could be precipitated using an immobilized BA, implying direct molecular interactions. Binding of BAs to LPS leads to an inhibition of LPS activity which was observed in vitro using a modified limulus amoebocyte lysate assay. Analysis of different BAs revealed clear structure-activity relationships with the classical β-BA as most potent derivative (IC(50)=1.8 μM). In RAW264.7 cells, LPS-induced expression of inducible nitric oxide synthase (iNOS, EC 1.14.13.39) was selectively inhibited by those BAs that interfered with LPS activity. In contrast, interferon-γ-induced iNOS induction was not affected by BAs. We conclude that structurally defined BAs are LPS inhibiting agents and we suggest that β-BA may contribute to the observed anti-inflammatory effects of BSE during infections by suppressing LPS activity.

Inhibition of microsomal prostaglandin E2 synthase-1 as a molecular basis for the anti-inflammatory actions of boswellic acids from frankincense

BACKGROUND AND PURPOSE

Frankincense, the gum resin derived from Boswellia species, showed anti-inflammatory efficacy in animal models and in pilot clinical studies. Boswellic acids (BAs) are assumed to be responsible for these effects but their anti-inflammatory efficacy in vivo and their molecular modes of action are incompletely understood.

EXPERIMENTAL APPROACH

A protein fishing approach using immobilized BA and surface plasmon resonance (SPR) spectroscopy were used to reveal microsomal prostaglandin E(2) synthase-1 (mPGES1) as a BA-interacting protein. Cell-free and cell-based assays were applied to confirm the functional interference of BAs with mPGES1. Carrageenan-induced mouse paw oedema and rat pleurisy models were utilized to demonstrate the efficacy of defined BAs in vivo.

KEY RESULTS

Human mPGES1 from A549 cells or in vitro-translated human enzyme selectively bound to BA affinity matrices and SPR spectroscopy confirmed these interactions. BAs reversibly suppressed the transformation of prostaglandin (PG)H(2) to PGE(2) mediated by mPGES1 (IC(50) = 3-10 µM). Also, in intact A549 cells, BAs selectively inhibited PGE(2) generation and, in human whole blood, β-BA reduced lipopolysaccharide-induced PGE(2) biosynthesis without affecting formation of the COX-derived metabolites 6-keto PGF(1α) and thromboxane B(2) . Intraperitoneal or oral administration of β-BA (1 mg·kg(-1) ) suppressed rat pleurisy, accompanied by impaired levels of PGE(2) and β-BA (1 mg·kg(-1) , given i.p.) also reduced mouse paw oedema, both induced by carrageenan.

CONCLUSIONS AND IMPLICATIONS

Suppression of PGE(2) formation by BAs via interference with mPGES1 contribute to the anti-inflammatory effectiveness of BAs and of frankincense, and may constitute a biochemical basis for their anti-inflammatory properties.

Boswellia resin: from religious ceremonies to medical uses; a review of in-vitro, in-vivo and clinical trials

Objectives

Despite its historical-religious, cultural and medical importance, Boswellia has not been thoroughly studied, and gaps still exist between our knowledge of the traditional uses of the resin and the scientific data available. Here we review the pharmacology of Boswellia resin and of the small molecules identified as the active ingredients of the resin.

Key findings

The resin of Boswellia species (‘frankincense’, ‘olibanum’) has been used as incense in religious and cultural ceremonies since the beginning of written history. Its medicinal properties are also widely recognized, mainly in the treatment of inflammatory conditions, as well as in some cancerous diseases, wound healing and for its antimicrobial activity. Until recently, work on Boswellia focused on the immunomodulatory properties of the resin and boswellic acids were considered to be the main, if not the only, active ingredients of the resin. Hence, this family of triterpenoids was investigated by numerous groups, both in vitro and in vivo. These compounds were shown to exert significant anti-inflammatory and pro-apoptotic activity in many assays: in vitro, in vivo and in clinical trials. We recently found incensole acetate and its derivatives, which are major components of Boswellia resin, to be nuclear factor-κB inhibitors, thus suggesting that they are, at least in part, responsible for its anti-inflammatory effects. Incensole acetate also exerts a robust neuroprotective effect after brain trauma in mice. Furthermore, it causes behavioural as well as anti-depressive and anxiolytic effects in mice. It is also a potent agonist of the transient receptor potential (TRP)V3 channel. It thus seems that incensole acetate and its derivatives play a significant role in the effects that Boswellia resin exerts on biological systems.

Conclusions

Altogether, studies on Boswellia resin have provided an arsenal of bio-active small molecules with a considerable therapeutic potential that is far from being utilized.

Boswellic acid inhibits expression of acid sphingomyelinase in intestinal cells

Background

Boswellic acid is a type of triterpenoids with antiinflammatory and antiproliferative properties. Sphingomyelin metabolism generates multiple lipid signals affecting cell proliferation, inflammation, and apoptosis. Upregulation of acid sphingomyelinase (SMase) has been found in several inflammation-related diseases such as inflammatory bowel diseases, atherosclerosis, and diabetes.

Methods

The present study is to examine the effect of 3-acetyl-11-keto-β-boswellic acids (AKBA), a potent boswellic acid, on acid SMase activity and expression in intestinal cells. Both transformed Caco-2 cells and non-transformed Int407 cells were incubated with AKBA. After incubation, the change of acid SMase activity was assayed biochemically, the enzyme protein was examined by Western blot, and acid SMase mRNA was quantified by qPCR.

Results

We found that AKBA decreased acid SMase activity in both intestinal cell lines in dose and time dependent manners without affecting the secretion of the enzyme to the cell culture medium. The effect of AKBA was more effective in the fetal bovine serum-free culture medium. Among different types of boswellic acid, AKBA was the most potent one. The inhibitory effect on acid SMase activity occurred only in the intact cells but not in cell-free extract in the test tubes. At low concentration, AKBA only decreased the acid SMase activity but not the quantity of the enzyme protein. However, at high concentration, AKBA decreased both the mass of acid SMase protein and the mRNA levels of acid SMase in the cells, as demonstrated by Western blot and qPCR, respectively. Under the concentrations decreasing acid SMase activity, AKBA significantly inhibited cell proliferation.

Conclusion

We identified a novel inhibitory effect of boswellic acids on acid SMase expression, which may have implications in human diseases and health.

Boswellic acids: a group of medicinally important compounds

This review, containing over 276 references, covers the progress made in the chemistry and bioactivity of this important group of triterpenoids. Though initially known for their anti-inflammatory and anti-arthritic activities through a unique 5-LO inhibition mechanism, boswellic acids have recently attained significance due to their anti-cancer properties. The phytochemistry and chemical modifications, including mechanism of action, are discussed.

Boswellic Acids Stimulate Arachidonic Acid Release and 12-Lipoxygenase Activity in Human Platelets Independent of Ca2+and Differentially Interact with Platelet-Type 12-Lipoxygenase

Boswellic acids inhibit the transformation of arachidonic acid to leukotrienes via 5-lipoxygenase but can also enhance the liberation of arachidonic acid in human leukocytes and platelets. Using human platelets, we explored the molecular mechanisms underlying the boswellic acid-induced release of arachidonic acid and the subsequent metabolism by platelet-type 12-li-poxygenase (p12-LO). Both beta-boswellic acid and 3-O-acetyl-11-keto-boswellic acid (AKBA) markedly enhanced the release of arachidonic acid via cytosolic phospholipase A2 (cPLA2), whereas for generation of 12-hydro(pero)xyeicosatetraenoic acid [12-H(P)ETE], AKBA was less potent than beta-boswellic acid and was without effect at higher concentrations (> or =30 microM). In contrast to thrombin, beta-boswellic acid-induced release of ara-chidonic acid and formation of 12-H(P)ETE was more rapid and occurred in the absence of Ca2+. The Ca2+-independent release of arachidonic acid and 12-H(P)ETE production elicited by beta-boswellic acid was not affected by pharmacological inhibitors of signaling molecules relevant for agonist-induced arachidonic acid liberation and metabolism. It is noteworthy that in cell-free assays, beta-boswellic acid increased p12-LO catalysis approximately 2-fold in the absence but not in the presence of Ca2+, whereas AKBA inhibited p12-LO activity. No direct modulatory effects of boswellic acids on cPLA2 activity in cell-free assays were evident. Therefore, immobilized KBA (linked to Sepharose beads) selectively precipitated p12-LO from platelet lysates but failed to bind cPLA2. Taken together, we show that boswellic acids induce the release of arachidonic acid and the synthesis of 12-H(P)ETE in human platelets by unique Ca2+-independent routes, and we identified p12-LO as a selective molecular target of boswellic acids.