A review on chemistry, source and therapeutic potential of lambertianic acid

Lambertianic acid (LA) is a diterpene bioactive compound mainly purified from different species of Pinus. It is an optical isomer of another natural compound daniellic acid and was firstly purified from Pinus lambertiana. LA can be synthesized in laboratory from podocarpic acid. It has been reported to have potential health benefits in attenuating obesity, allergies and different cancers including breast, liver, lung and prostate cancer. It exhibits anticancer properties through inhibiting cancer cell proliferation and survival, and inducing apoptosis, targeting major signalling components including AKT, AMPK, NFkB, COX-2, STAT3, etc. Most of the studies with LA were done using in vitro models, thus warranting future investigations with animal models to evaluate its pharmacological effects such as antidiabetic, anti-inflammatory and neuroprotective effects as well as to explore the underlying molecular mechanisms and toxicological profile. This review describes the chemistry, source, purification and therapeutic potentials of LA and it can therefore be a suitable guideline for any future study with LA.

Suppression of STAT3 Phosphorylation and RelA/p65 Acetylation Mediated by MicroRNA134 Plays a Pivotal Role in the Apoptotic Effect of Lambertianic Acid

As p300-mediated RelA/p65 hyperacetylation by signal transducers and activators of transcription 3 (STAT3) is critical for NF-κB activation, in the current study, the apoptotic mechanism of lambertianic acid (LA) was explored in relation to STAT3 phosphorylation and RelA/p65 acetylation in MCF-7, DU145, PC-3, and MDA-MB-453 cells. LA significantly increased the cytotoxicity, sub G 1 population, and the cleavage of poly (ADP-ribose) polymerase (PARP) in MDA-MB-453 or PC-3 cells (STAT3 mutant), more than in the MCF-7 or DU145 cells (STAT3 wild). Consistently, LA inhibited the phosphorylation of STAT3 and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and disrupted the interaction between p-STAT3, p300, NF-κB, and RelA/p65 acetylation (Ac-RelA/p65) in the MCF-7 and DU145 cells. Also, LA reduced the nuclear translocation of STAT3 and NF-κB via their colocalization, and also suppressed the protein expression of XIAP, survivin, Bcl-2, Bcl-xL, vascular endothelial growth factor (VEGF), Cox-2, c-Myc and mRNA expression of interleukin 6 (IL-6), and tumor necrosis factor-α (TNF-α) in MCF-7 cells. Conversely, IL-6 blocked the ability of LA to suppress the cytotoxicity and PARP cleavage, while the depletion of STAT3 or p300 enhanced the PARP cleavage of LA in the MCF-7 cells. Notably, LA upregulated the level of miRNA134 and so miRNA134 mimic attenuated the expression of pro-PARP, p-STAT3, and Ac-RelA, while the miRNA134 inhibitor reversed the ability of LA to reduce the expression of Ac-RelA and pro-PARP in MCF-7 cells. Overall, these findings suggest that LA induced apoptosis via the miRNA-134 mediated inhibition of STAT3 and RelA/p65 acetylation.

Highly Selective Gold-Catalyzed Cycloisomerization of Furanolabdanoid Dialkynes with Alkynyl Substituents in the Furan Ring

Aim and Objective: We studied the synthesis of new groups of functionalized isobenzofurans and isoindolines by selective gold catalyzed cycloisomerization of some new optically active furandialkynes derived from the natural furanolabdanoid lambertianic acid. Functionalized isobenzofurans and isoindolines are considered as privileged structures that are currently experiencing a renewed interest in medicinal chemistry. Materials and Methods: Using the AuCl3-catalyzed cycloisomerization of furanolabdanoid dialkynes we synthesized several new groups of biologically interested isobenzofurans and isoindolines with labdanoid substitution. The structure of all new compounds was proven by elemental and spectral analysis: IR, mass-, and NMR data. Results: The synthesis of 15,16-dialkynyl substituted furanolabdanoids was carried out. Au(III)-Catalyzed cycloisomerization of those compounds proceeded highly selectively with the formation of optically active 4- substituted 7-hydroxy-3(6)-propargylaminomethylisobenzofurans or 7-hydroxy-3(6)-propargyloxymethylisoindolines. The cycloisomerization of the 15-(prop-2-yn-1-yloxymethyl)-16-((N-p-toluenesulfonyl)-prop- 2-yn-1-ylaminomethyl)labdatriene proceeded in part on the 15 position and involved the previously unknown intramolecular transfer of N-(p-toluenesulfonyl)propargylaminomethyl substituent to the oxygen in the stage of formation of an aromatic ring. A feasible reaction mechanism for this transformation is presented. It was revealed that the conversion of labdanoid furan-15-ynes to 1,3-dihydroisobenzofurans depends on the nature of the substituent in the 16 position of the furanolabdanoid. Conclusions: The present study sheds light on the Au(III)-catalyzed cycloisomerization of new group of highly functionalized furandialkynes. Also, new groups of alkynyloxymethyl or alkynylaminomethyl substituted optically active isobenzofurans and isoindolines were obtained and fully characterized.

Lambertianic Acid Sensitizes Non-Small Cell Lung Cancers to TRAIL-Induced Apoptosis Via Inhibition of XIAP/NF-kB and Activation of Caspases and Death Receptor 4

Lambertianic acid (LA) is a biologically active compound from the leaves of Pinus koraiensis. In the present study, apoptotic mechanisms of LA plus TNF-related apoptosis-inducing ligand (TRAIL) were elucidated in non-small cell lung cancer cells (NSCLCs). Cytotoxicity assay, flow cytometry, immunoprecipitation and Western blotting were performed. Here, combined treatment of LA and TRAIL increased cytotoxicity, sub-G1 population and cleaved poly (ADP-ribose) polymerase (PARP) and caspase3/8/9 in A549 and H1299 cells compared to LA or TRAIL alone. Furthermore, combined treatment of LA and TRAIL significantly decreased anti-apoptotic proteins such as B-cell lymphoma 2 (Bcl-2), Fas-like inhibitor protein (FLIP) and X-linked inhibitor of apoptosis protein (XIAP) and enhanced the activation of pro-apoptotic proteins Bid compared to LA or TRAIL alone. In addition, combined treatment of LA and TRAIL upregulated the expression of Death receptor 4 (DR4) and downregulated phosphorylation of nuclear factor kappa-light-chain-enhancer of activated B cells (p-NF-B), inhibitory protein of kB family (p-IB) and FLIP in A549 and H1299 cells along with disrupted binding of XIAP with caspase3 or NF-B. Overall, these findings suggest that lambertianic acid enhances TRAIL-induced apoptosis via inhibition of XIAP/NF-B in TRAIL resistant NSCLCs.