Chemical transformation and biological activities of ambrein, a major product of ambergris from Physeter macrocephalus (sperm whale)

Metabolic engineering of Saccharomyces cerevisiae for high-level production of (+)-ambrein from glucose

(+)-Ambrein is the primary component of ambergris, a rare product found in sperm whales (Physeter microcephalus). Microbial production using sustainable resources is a promising way to replace animal extraction and chemical synthesis. We constructed an engineered yeast strain to produce (+)-ambrein de novo. Squalene is a substrate for the biosynthesis of (+)-ambrein. Firstly, strain LQ2, with a squalene yield of 384.4 mg/L was obtained by optimizing the mevalonate pathway. Then we engineered a method for the de novo production of (+)-ambrein using glucose as a carbon source by overexpressing codon-optimized tetraprenyl-β-curcumene cyclase (BmeTC) and its double mutant enzyme (BmeTCY167A/D373C), evaluating different promoters, knocking out GAL80, and fusing the protein with BmeTC and squalene synthase (AtSQS2). Nevertheless, the synthesis of (+)-ambrein is still limited, causing low catalytic activity in BmeTC. We carried out a protein surface amino acid modification of BmeTC. The dominant mutant BmeTCK6A/Q9E/N454A for the first step was obtained to improve its catalytic activity. The yield of (+)-ambrein increased from 35.2 to 59.0 mg/L in the shake flask and finally reached 457.4 mg/L in the 2 L fermenter, the highest titer currently available for yeast. Efficiently engineered strains and inexpensive fermentation conditions for the industrial production of (+)-ambrein. The metabolic engineering tools provide directions for optimizing the biosynthesis of other high-value triterpenes.

Occurrence of Marine Ingredients in Fragrance: Update on the State of Knowledge

The fragrance field of perfumes has attracted considerable scientific, industrial, cultural, and civilizational interest. The marine odor is characterized by the specific smell of sea breeze, seashore, algae, and oyster, among others. Marine odor is a more recent fragrance and is considered as one of the green and modern fragrances. The smells reproducing the marine environment are described due to their content of Calone 1951 (7-methyl-2H-1,5-benzodioxepin-3(4H)-one), which is a synthetic compound. In addition to the synthetic group of benzodioxepanes, such as Calone 51 and its derivatives, three other groups of chemical compounds seem to represent the marine smell. The first group includes the polyunsaturated cyclic ((+)-Dictyopterene A) and acyclic (giffordene) hydrocarbons, acting as pheromones. The second group corresponds to polyunsaturated aldehydes, such as the (Z,Z)-3,6-nonadienal, (E,Z)-2,6-nonadienal, which are most likely derived from the degradation of polyunsaturated fatty acids. The third group is represented by small molecules such as sulfur compounds and halogenated phenols which are regarded as the main flavor compounds of many types of seafood. This review exposes, most notably, the knowledge state on the occurrence of marine ingredients in fragrance. We also provide a detailed discussion on several aspects of essential oils, which are the most natural ingredients from various marine sources used in fragrance and cosmetics, including synthetic and natural marine ingredients.

Construction of an artificial system for ambrein biosynthesis and investigation of some biological activities of ambrein

Ambergris, a sperm whale metabolite, has long been used as a fragrance and traditional medication, but it is now rarely available. The odor components of ambergris result from the photooxidative degradation of the major component, ambrein. The pharmacological activities of ambergris have also been attributed to ambrein. However, efficient production of ambrein and odor compounds has not been achieved. Here, we constructed a system for the synthesis of ambrein and odor components. First, we created a new triterpene synthase, “ambrein synthase,” for mass production of ambrein by redesigning a bacterial enzyme. The ambrein yields were approximately 20 times greater than those reported previously. Next, an efficient photooxidative conversion system from ambrein to a range of volatiles of ambergris was established. The yield of volatiles was 8–15%. Finally, two biological activities, promotion of osteoclast differentiation and prevention of amyloid β-induced apoptosis, were discovered using the synthesized ambrein.

First evidence of terrestrial ambrein formation in human adipocere

To date, the only known occurrence of ambrein, an important perfumery organic molecule, is in coproliths found in about one in a hundred sperm whales. Jetsam ambergris coproliths from the whale are also found occasionally on beaches worldwide. Here we report on the surprising occurrence of ambrein in human adipocere. Adipocere is a waxy substance formed post-mortem during incomplete anaerobic decomposition of soft tissues. Adipocere samples obtained from grave exhumations were analysed using gas chromatography-mass spectrometry (GC-MS). In addition to the typical fatty acids of adipocere, lesser amounts of ambrein were identified in the samples, in abundances similar to those of the major accompanying faecal steroids. The distribution of these compounds suggests that ambrein was produced post-mortem during the microbial decomposition of faecal residues and tissues. It is assumed that the adipocere matrix of saturated fatty acidsaided the preservation of ambrein over extended periods of time, because adipocere is stable against degradation. The association of ambrein formation in ageing faecal material, under moist, oxygen-depleted conditions, now requires more attention in studies of other mammalian and geological samples. Indeed, ambrein and its transformation products may be useful novel chemical indicators of aged faecal matter and decomposed bodies.

Cyclohexylmethyl Flavonoids Suppress Propagation of Breast Cancer Stem Cells via Downregulation of NANOG

Breast cancer stem cells (CSCs) are highly tumorigenic and possess the capacity to self-renew. Recent studies indicated that pluripotent gene NANOG involves in regulating self-renewal of breast CSCs, and expression of NANOG is correlated with aggressiveness of poorly differentiated breast cancer. We initially confirmed that breast cancer MCF-7 cells expressed NANOG, and overexpression of NANOG enhanced the tumorigenicity of MCF-7 cells and promoted the self-renewal expansion of CD24^−/lowCD44⁺ CSC subpopulation. In contrast, knockdown of NANOG significantly affected the growth of breast CSCs. Utilizing flow cytometry, we identified five cyclohexylmethyl flavonoids that can inhibit propagation of NANOG-positive cells in both breast cancer MCF-7 and MDA-MB231 cells. Among these flavonoids, ugonins J and K were found to be able to induce apoptosis in non-CSC populations and to reduce self-renewal growth of CD24^−/lowCD44⁺ CSC population. Treatment with ugonin J significantly reduced the tumorigenicity of MCF-7 cells and efficiently suppressed formation of mammospheres. This suppression was possibly due to p53 activation and NANOG reduction as either addition of p53 inhibitor or overexpression of NANOG can counteract the suppressive effect of ugonin J. We therefore conclude that cyclohexylmethyl flavonoids can possibly be utilized to suppress the propagation of breast CSCs via reduction of NANOG.

Use of the Plant Bellardia trixago for the Enantiospecific Synthesis of Odorant Products

An easy procedure to obtain extracts enriched in trixagol monomalonylesther (1) from aerial parts of the plant Belladia trixago chemotype Trix was developed. Preparation of (+)-dihydro-γ-ionone (4) was carried out directly from the extracts with good yields by selective oxidation. Other interesting odorant products as α-ambrinol (5), ambraldehyde (6) and the tricyclic compound 7 were synthesized very efficiently using (4) as intermediate.

Anti-inflammatory flavonoids from the rhizomes of Helminthostachys zeylanica

Eight new prenylated flavonoids, ugonins M-T (1-8), together with five known compounds, ugonins J-L (9-11), 5,4'-dihydroxy-4'',4''-dimethyl-5''-methyl-5''H-dihydrofurano[2'',3'':6,7]flavanone, and quercetin, were isolated and purified from the rhizomes of Helminthostachys zeylanica. The structures of the new isolates were elucidated by spectroscopic and chemical methods. Compounds 1, 3, 5, 7, 8, and 11 showed inhibition of superoxide anion generation and elastase release by human neutrophils in response to formyl-l-methionyl-l-leucyl-l-phenylalanine/cytochalasin B (FMLP/CB).