A novel Ca2+-signal transduction inhibitor, kujigamberol C, isolated from Kuji amber.

A novel labdane type diterpenoid, 15-nor-8-labden-13-ol, named kujigamberol C, was isolated from Kuji amber using a modified isolation method to increase the yield of biologically active compounds. The structure was determined using HREIMS, 1D and 2D NMR. Kujigamberol C showed growth-restoring activity against mutant yeast via Ca2+-signal transduction.

Isolation of a spirolactone norditerpenoid as a yeast Ca2+ signal transduction inhibitor from Kuji amber and evaluation of its effects on PPM1A activity.

A different type of biologically active compound from Kuji amber (Late Cretaceous, Japan) before the K-Pg boundary [65 million years ago (Ma)] was isolated based on the growth-restoring activity of a mutant yeast involving Ca2+ signal transduction. It was identified as a spirolactone norditerpenoid, (4R*, 5S*, 8R*, 9R*, 10S*)-14,15,16,19-tetranor-labdan-13,9-olide (1) from spectral analyses with high-resolution electron ionization mass spectrometry (HREIMS), 1D and 2D nuclear magnetic resonance (NMR). Although the planar structure of 1 is known as an artificial derivative from marrubiin, it was isolated as a natural product from Kuji amber and its structure was elucidated for the first time. It had a growth-restoring activity against the mutant yeast through the direct or indirect inhibition of calcineurin activity [protein phosphatase, Mg2+/Mn2+-dependent 1A (PPM1A) activation]. Furthermore, the compound had potent inhibitory effect against the degranulation of rat basophilic leukemia 2H3 (RBL-2H3) cells.

Anti-allergy activities of Kuji amber extract and kujigamberol.

Amber is fossilized tree resin and several biologically active compounds were isolated from ambers using the growth-restoring activity of the mutant yeast [Saccharomyces cerevisiae (zds1∆ erg3∆ pdr1∆ pdr3∆)] involving Ca2+-signal transduction. The aim of this study is to investigate the anti-allergic effect of both the methanol extract of Kuji amber (MEKA) and its main biologically active constituent, kujigamberol (15,20-dinor-5,7,9-labdatrien-18-ol) having activity against the mutant yeast. Both MEKA and kujigamberol inhibited the degranulation of RBL-2H3 cells by stimulation of thapsigargin (Tg) (IC50 = 15.0 µg/ml and 29.1 µM) and A23187 (IC50 = 19.6 µg/ml and 24.9 µM) without cytotoxicity, but not by stimulation of IgE + DNP-BSA (Ag) (IC50 > 50.0 µg/ml and 50.0 µM). However, both inhibited Ca2+-influx in RBL-2H3 cells by all three stimulations in a dose dependent manner. Leukotriene C4 production in RBL-2H3 cells stimulated by A23187 was also inhibited by both through the inhibition of ERK1/2 phosphorylation. In an ovalbumin-induced rhinitis model of guinea pigs, nasal administration of MEKA and kujigamberol inhibited nasal blockade in a dose-dependent manner and the effect was about 5 times potent than that of a steroid clinical drug, mometasone furoate. The growth-restoring activity of MEKA and kujigamberol against the mutant yeast is involved in the anti-allergic activities against cells and animals, and both are expected to be candidates for the development of new anti-allergy agents.