Differential cytotoxic activity of the petroleum ether extract and its furanosesquiterpenoid constituents from Commiphora molmol resin

Terpenoids from Myrrh and Their Cytotoxic Activity against HeLa Cells

The oleo-gum resin of Commiphora myrrha (Nees) Engl. has a long history of medicinal use, although many of its constituents are still unknown. In the present investigation, 34 secondary metabolites were isolated from myrrh resin using different chromatographic techniques (silica flash chromatography, CPC, and preparative HPLC) and their structures were elucidated with NMR spectroscopy, HRESIMS, CD spectroscopy, and ECD calculations. Among the isolated substances are seven sesquiterpenes (1-7), one disesquiterpene (8), and two triterpenes (23, 24), which were hitherto unknown, and numerous substances are described here for the first time for C. myrrha or the genus Commiphora. Furthermore, the effects of selected terpenes on cervix cancer cells (HeLa) were studied in an MTT-based in vitro assay. Three triterpenes were observed to be the most toxic with moderate IC₅₀ values of 60.3 (29), 74.5 (33), and 78.9 µM (26). Due to the different activity of the structurally similar triterpenoids, the impact of different structural elements on the cytotoxic effect could be discussed and linked to the presence of a 1,2,3-trihydroxy substructure in the A ring. The influence on TNF-α dependent expression of the intercellular adhesion molecule 1 (ICAM-1) in human microvascular endothelial cells (HMEC-1) was also tested for 4-6, 9-11, 17, 18, 20, and 27 in vitro, but revealed less than 20% ICAM-1 reduction and, therefore, no significant anti-inflammatory activity.

Phytochemical Composition of Commiphora Oleogum Resins and Their Cytotoxicity against Skin Cancer Cells

Oleogum resins of the genus Commiphora have been used in traditional medicines for centuries. More than 200 Commiphora species exhibit highly variable phytochemical compositions. A novel highly selective, sensitive, accurate HPLC-MS/MS method was developed and validated to quantify five characteristic phytosteroids and furanosesquiterpenoids, namely (E)-guggulsterone, (Z)-guggulsterone, curzerenone, furanoeudesma-1,3-diene, and myrrhone. The resulting contents and additionally GC analysis were used to classify and differentiate Commiphora oleogum resins of the species C. myrrha, C. erythraea, C. mukul, C. holtziana, C. confusa, and C. kua, as well as unspecified resins. Interestingly, a Commiphora sample from Ogaden, Ethiopia, comprised 446 ng/mg guggulsterones presumed to be unique to C. mukul from the Indian subcontinent. However, Commiphora from Ogaden differed considerably from C. mukul in respect to guggulsterones isomer’s ratio. Moreover, the cytotoxicity of Commiphora extracts, essential oils, botanical drugs containing Commiphora, and pure compounds against the epidermoid carcinoma A431, malignant melanoma RPMI-7951 and SK-MEL-28 cells was investigated in vitro. Thereby, especially C. mukul extract and C. myrrha essential oil exhibited high cytotoxicity against skin cancer cells with IC₅₀ of 2.9–10.9 µg/mL, but were less toxic to normal keratinocytes. In summary, Commiphora oleogum resins and its phytochemicals warrant further investigation aiming at chemotaxonomical classification as well as application in skin cancer treatment.

Anti-Inflammatory and Barrier-Stabilising Effects of Myrrh, Coffee Charcoal and Chamomile Flower Extract in a Co-Culture Cell Model of the Intestinal Mucosa

Recent clinical evidence suggests the efficacy of a traditional herbal medicinal product containing myrrh (Commiphora molmol Engl.), coffee charcoal (Coffea arabica L.) and chamomile flower dry extract (Matricaria chamomilla L.) in the therapy of inflammatory bowel diseases (IBD). However, the mechanisms of action in this context have not been entirely elucidated. The present study aimed to evaluate the effects of myrrh, coffee charcoal and chamomile flower extract on the inflammatory cross talk between immune and intestinal epithelial cells together with the resulting intestinal barrier disorders. A complex co-culture cell model consisting of intestinal epithelial cell (IEC) monolayers (Caco-2, HT29-MTX-E12) and macrophages (THP-1) was established for the simultaneous investigation of these two IBD characteristics. The lipopolysaccharide (LPS) activation of the macrophages led to a pro-inflammatory mediator release and thereby an inflammatory stimulation of IECs with chemokine release and reduced barrier function. The effects of the individual plant extracts and a ternary combination on inflammatory mediator release (IL-6, TNF, IL-8, MCP-1, PGE2) was quantified by ELISA. The transepithelial electrical resistance (TEER) of IEC monolayers was measured to evaluate the effects on the barrier function. Budesonide served as a positive control. All three plant extracts exhibited anti-inflammatory properties via the inhibition of the inflammatory mediator release to a varying extent. An intestinal barrier stabilising effect was observed for myrrh and coffee charcoal. Myrrh exerted the most distinct pharmacological activity. Dose reducing and synergistic interactions emerged within the threefold combination. Thus, our results provide a mechanistic basis for the use of the herbal combination of myrrh, coffee charcoal and chamomile flower extract in IBD treatment and underline the potential benefits of the phytotherapeutic multi-component/multi-target approach in this complex pathogenesis.

Total synthesis, structural revision and biological evaluation of γ-elemene-type sesquiterpenes

Total synthesis and absolute configuration confirmation of γ-elemene-type sesquiterpenes, which possess vast potential for biological activities, was investigated based on a convergent synthetic strategy. A key intermediate with all functional groups of this family of natural products was accessed by an intermolecular aldol reaction and then an acetylation of a known ketone (12) derived from commercially available verbenone. The versatile intermediate can be easily transformed into structurally different γ-elemene-type sesquiterpenes based on control of base-promoted cyclization manipulation in different solvents. The utility of this robust approach is illustrated by the first syntheses of elema-1,3,7(11),8-tetraen-8,12-lactam (4') and 8β-methoxy-isogermafurenolide (6a), as well as the syntheses of elem-1,3,7,8-tetraen-8,12-olide (3) and hydroxyisogermafurenolide (5) in only 6 or 7 steps. In addition, the structure of the reported 5βH-elem-1,3,7,8-tetraen-8,12-olide (1) was revised as elem-1,3,7,8-tetraen-8,12-olide (3) by comparison of their identified datum, and the absolute configuration of elema-1,3,7(11),8-tetraen-8,12-lactam was confirmed as 4'. Furthermore, the inhibitory effect of all synthesized natural compounds and their natural analogues on cancer cell proliferation was evaluated. Among them compounds 3, 4 and 4' were found to possess potent inhibitory activity against Kasumi-1 and Pfeiffer. Meanwhile, preliminary structure-activity relationships for these compounds are discussed.