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

Abstract

Introduction: Cancer has been identified to be the second major cause of death internationally as exemplified by ca. 9.6 million deaths in 2018 along with ca. 18 million new patients in 2018 that have been recorded. Natural boswellic acids (BAs) and their source, frankincense, have been reported to possess in vitro and in vivo anticancer effects toward various cancer cells. Areas covered: This comprehensive review focuses on the importance of boswellic acids (BAs) for the establishment of future treatments of cancer. Moreover, potent semisynthetic derivatives of BAs have been described along with their mode of action. In addition, important structural features of the semisynthetic BAs required for cytotoxic effects are also discussed. Expert opinion: Numerous semisynthetic BAs illustrate excellent cytotoxic effects. Of note, compounds bearing cyanoenone moieties in ring A, endoperoxides and hybrids display increased and more potent cytotoxic effects compared with other semisynthetic BAs. Moreover, BAs have the potential to conjugate or couple with other anticancer compounds to synergistically increase their combined anticancer effects. In addition, to get derived BAs to become lead anticancer compounds, future research should focus on the preparation of ring A cyanoenones, endoperoxides, and C-24 amide analogs.

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

“…Cycloorbicoside B (10) displayed the highest activity in this assay (10.60 mg TE/g), followed by the compounds 3 (6.95 mg TE/g), 6 (6.08 mg TE/g), and 4 (6.05 mg TE/g). At the other end, oleanolic acid (14) revealed no activity in this assay (Figure 2A).…”

“…This was followed by ursolic acid (15), cycloalpioside D-2 ,3 ,4 ,7-tetraacetate (7), and 3-O-β-D-xylopyranoside-(23R,24S)-16β,23;16α,24-diepoxycycloart-25(26)-en-3β,7β-diol 7monoacetate (4), displaying activities of 30.2, 25.4, and 21.9 mg EDTAE/g, respectively. However, oleanolic acid (14) showed the lowest activity in this assay, which was equal to 3.05 mg EDTAE/g (Table 1).…”

“…Fifteen triterpenes were used in this study and they are illustrated in Figure 1 9), cycloorbicoside B (10), cyclosiversioside E (11), astragaloside IV (cyclosieversioside F or astrasieversianin XIV) (12), cyclosiversioside H (13), oleanolic acid (14), and ursolic acid (15).…”

“…They were cycloorbicoside A (1), cycloorbicoside A-7-monoacetate ( 2 9), cycloorbicoside B (10), cyclosiversioside E (11), astragaloside IV (syn. cyclosieversioside F, astrasieversianin XIV) (12), cyclosiversioside H (13), oleanolic acid (14), and ursolic acid (15).…”

“…Terpenes include several classes represented by mono and sesquiterpene components that prevail in essential oils, diterpenes, and triterpenes (with steroids) of different types, as well as in tetraterpene carotenoids and polyterpenes. Nowadays, there is an increasing interest in natural triterpenoids due to their outstanding biological activities as exemplified by reported anticancer, antiviral, bactericidal, spermicidal, anti-allergic, fungicidal, and cardiovascular protective effects [13][14][15][16][17].…”