Sclareol

Mol Med Rep. 2015 Jun;11(6):4273-8.

Sclareol, a plant diterpene, exhibits potent antiproliferative effects via the induction of apoptosis and mitochondrial membrane potential loss in osteosarcoma cancer cells.[Pubmed: 25672419]

The objective of the current study was to evaluate the antiproliferative activity of Sclareol against MG63 osteosarcoma cells. A 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide assay was used to evaluate the cell viability of cells following treatment with Sclareol.
METHODS AND RESULTS:
The extent of cell death induced by Sclareol was evaluated using a lactate dehydrogenase (LDH) assay. The effect of Sclareol on cell cycle progression and mitochondrial membrane potential (ΛΨm) was evaluated with flow cytometry using the DNA‑binding fluorescent dyes propidium iodide and rhodamine‑123, respectively. Fluorescence microscopy was used to detect the morphological changes in the MG63 osteosarcoma cancer cells and the appearance of apoptotic bodies following Sclareol treatment. The results revealed that Sclareol induced dose‑ and time‑dependent growth inhibition of MG63 cancer cells with an IC50 value of 65.2 µM following a 12‑h incubation. Furthermore, Sclareol induced a significant increase in the release of LDH from MG63 cell cultures, which was much more pronounced at higher doses. Fluorescence microscopy revealed that Sclareol induced characteristic morphological features of apoptosis and the appearance of apoptotic bodies. Flow cytometry revealed that Sclareol induced G1‑phase cell cycle arrest, which showed significant dose‑dependence. Additionally, Sclareol induced a progressive and dose‑dependent reduction in the ΛΨm.
CONCLUSIONS:
In summary, Sclareol inhibits the growth of osteosarcoma cancer cells via the induction of apoptosis, which is accompanied by G1‑phase cell cycle arrest and loss of ΛΨm.

Mol Plant Microbe Interact. 2015 Apr;28(4):398-407.

Sclareol induces plant resistance to root-knot nematode partially through ethylene-dependent enhancement of lignin accumulation.[Pubmed: 25423264]

The root-knot nematode (RKN) is one of the most devastating parasitic nematodes of plants. Although some secondary metabolites released by the host plant play roles as defense substances against parasitic nematodes, the mechanism underlying the induction of such defense responses is not fully understood.
METHODS AND RESULTS:
We found that Sclareol, a natural diterpene known as an antimicrobial and defense-related molecule, inhibited RKN penetration of tomato and Arabidopsis roots. Sclareol induced genes related to ethylene (ET) biosynthesis and signaling and phenylpropanoid metabolism in Arabidopsis roots. In roots of ein2-1, an ET-insensitive mutant line, both Sclareol-induced inhibition of RKN penetration and Sclareol-induced enhancement of lignin accumulation were abolished. A mutant defective in lignin accumulation did not exhibit such inhibition. Sclareol also activated MPK3 and MPK6, Arabidopsis mitogen-activated protein kinases whose activation is required for triggering ET biosynthesis. Sclareol-induced inhibition of RKN penetration was exhibited by mutants of neither MPK3 nor MPK6. Treatment with a biosynthetic precursor of ET was insufficient compared with Sclareol treatment to inhibit RKN penetration, suggesting the existence of an ET-independent signaling pathway leading to RKN resistance.
CONCLUSIONS:
These results suggested that Sclareol induced resistance to RKN penetration partially through ET-dependent accumulation of lignin in roots.

Iran J Immunol. 2013 Mar;10(1):10-21.

Sclareol reduces CD4+ CD25+ FoxP3+ Treg cells in a breast cancer model in vivo.[Pubmed: 23502334]

Sclareol is a phytochemical used in people's diet in Southeast Asia. To investigate the immunotherapeutic effectiveness of Sclareol against breast cancer by direct intraperitoneal injection.
METHODS AND RESULTS:
Sclareol was isolated and purified from Salvia sclarea. Effect of Sclareol on cell growth inhibition was evaluated by MTT assay. Intraperitoneally injected Sclareol effects on reducing the tumor volume and shifting the cytokine profile were investigated. We also assessed if intraperitoneally injected Sclareol could improve the outcome of cancer therapy through suppressing the regulatory T cells.The results confirmed a significant decrease in the tumor size. Furthermore, a significant decrease in the level of IL-4 and an increase in the level of IFN-γ were noticed in the intraperitoneally injected Sclareol group (p<0.05). It was also observed that the splenocytes of treated animals significantly increase in cell proliferation assay. Moreover, measurements of splenic T regulatory cell indicated that intraperitoneally injected Sclareol significantly decreased the number of splenic T regulatory cell.
CONCLUSIONS:
Our results suggest that Sclareol, by reducing Treg cells frequency and also tumor size can enhance the effect of cancer therapy as an immuno-stimulant.

Int J Clin Exp Pathol. 2015 Mar 1;8(3):2365-74.

Sclareol exerts anti-osteoarthritic activities in interleukin-1β-induced rabbit chondrocytes and a rabbit osteoarthritis model.[Pubmed: 26045743]

Sclareol is a natural product initially isolated form Salvia sclarea which possesses immune-regulation and anti-inflammatory activities. However, the anti-osteoarthritic properties of Sclareol have not been investigated. The present study is aimed at evaluating the potential effects of Sclareol in interleukin-1β (IL-1β)-induced rabbit chondrocytes as well as an experimental rabbit knee osteoarthritis model induced by anterior cruciate ligament transection (ACLT).
METHODS AND RESULTS:
Cultured rabbit chondrocytes were pretreated with 1, 5 and 10 μg/mL Sclareol for 1 h and followed by stimulation of IL-1β (10 ng/mL) for 24 h. Gene expression of matrix metalloproteinase-1 (MMP-1), MMP-3, MMP-13, tissue inhibitors of metalloproteinase-1 (TIMP-1), inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 was determined by quantitative real-time polymerase chain reaction (qRT-PCR). MMP-3, TIMP-1, iNOS and COX-2 proteins were measured by Western blotting. Enzyme-linked immunosorbent assay (ELISA) was applied for nitric oxide (NO) and prostaglandin E2 (PGE2) assessment. For the in vivo study, rabbits received six weekly 0.3 mL Sclareol (10 μg/mL) intra-articular injections in the knees four weeks after ACLT surgery. Cartilage was harvested for measurement of MMP-1, MMP-3, MMP-13, TIMP-1, iNOS and COX-2 by qRT-PCR, while femoral condyles were used for histological evaluation. The in vitro results we obtained showed that Sclareol inhibited the MMPs, iNOS and COX-2 expression on mRNA and protein levels, while increased the TIMP-1 expression. And over-production of NO and PGE2 was also suppressed. For the in vivo study, both qRT-PCR results and histological evaluation confirmed that Sclareol ameliorated cartilage degradation.
CONCLUSIONS:
Hence, we speculated that Sclareol may be an ideal approach for treating osteoarthritis.