BACKGROUND: Friedelin is a pharmacologically valuable pentacyclic triterpenoid with anti-inflammatory, anticancer, antiviral, and antiobesity properties. Conventional methods of friedelin production rely on solvent-intensive extraction from plant biomass, which is often expensive, inefficient, and environmentally unsustainable. Phaeodactylum tricornutum, a model marine diatom with a unique chimeric sterol biosynthetic pathway and native oxidosqualene accumulation, presents a promising platform for heterologous triterpenoid biosynthesis. RESULTS: In this study, the TwOSC4 gene from Tripterygium wilfordii, which encodes friedelin synthase, was successfully expressed in P. tricornutum via biolistic transformation. As a result, two transgenic strains, Pt-OSC4-20 and Pt-OSC4-48, were confirmed to express TwOSC4 at both transcript and protein levels. Liquid chromatography–quadrupole time-of-flight mass spectrometry (LC-QTOF/MS) analysis validated friedelin production in these strains, with a baseline accumulation of 26 ng/mL under standard conditions. Upon treatment with Ro 48-8071, an oxidosqualene cyclase inhibitor that suppresses endogenous sterol biosynthesis, friedelin production increased up to 55 ng/mL. Nile red staining revealed increased lipid droplet formation in the transgenic strains, suggesting the possible intracellular storage of friedelin. Importantly, transgene expression did not impair cell growth, indicating the metabolic compatibility of the host with exogenous triterpenoid synthesis. CONCLUSIONS: This is the first study to demonstrate successful biosynthesis of friedelin in a microalgal system, highlighting the potential of P. tricornutum as a sustainable phototrophic chassis for the production of plant-derived triterpenoids. Unlike yeast-based systems, which require extensive metabolic amplification, P. tricornutum enables simpler genetic engineering and simultaneous coproduction of valuable compounds, such as fucoxanthin and Omega-3 Eicosapentaenoic Acid (EPA). These findings lay the groundwork for further strain optimization aimed at increasing friedelin yield and broadening the scope of triterpenoid biosynthesis in microalgae.

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Pharmaceutical companies are investigating more source matrices for natural bioactive chemicals. Friedelin (friedelan-3-one) is a pentacyclic triterpene isolated from various plant species from different families as well as mosses and lichen. The fundamental compounds of these friedelane triterpenoids are abundantly found in cork tissues and leaf materials of diverse plant genera such as Celastraceae, Asteraceae, Fabaceae, and Myrtaceae. They possess many pharmacological effects, including anti-inflammatory, antioxidant, anticancer, and antimicrobial activities. Friedelin also has an anti-insect effect and the ability to alter the soil microbial ecology, making it vital to agriculture. Ultrasound, microwave, supercritical fluid, ionic liquid, and acid hydrolysis extract friedelin with reduced environmental impact. Recently, the high demand for friedelin has led to the development of CRISPR/Cas9 technology and gene overexpression plasmids to produce friedelin using genetically engineered yeast. Friedelin with low cytotoxicity to normal cells can be the best phytochemical for the drug of choice. The review summarizes the structural interpretation, biosynthesis, physicochemical properties, quantification, and various forms of pharmacological significance.

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Friedelin, the most rearranged pentacyclic triterpene, also exhibits remarkable pharmacological and anti-insect activities. In particular, celastrol with friedelin as the skeleton, which is derived from the medicinal plant Tripterygium wilfordii , is a promising drug due to its anticancer and antiobesity activities. Although a previous study achieved friedelin production using engineered Saccharomyces cerevisiae , strains capable of producing high-level friedelin have not been stably engineered. In this study, a combined strategy was employed with integration of endogenous pathway genes into the genome and knockout of inhibiting genes by CRISPR/Cas9 technology, which successfully engineered multiple strains. After introducing an efficient Tw OSC1 T502E , all strains with genetic integration ( tHMG1 , ERG1 , ERG20 , ERG9 , POS5 , or UPC2.1 ) showed a 3.0∼6.8-fold increase in friedelin production compared with strain BY4741. Through further double knockout of inhibiting genes, only strains GD1 and GD3 produced higher yields. Moreover, strains GQ1 and GQ3 with quadruple mutants ( bts1 ; rox1 ; ypl062w ; yjl064w ) displayed similar increases. Finally, the dominant strain GQ1 with Tw OSC1 T502E was cultured in an optimized medium in shake flasks, and the final yield of friedelin reached 63.91 ± 2.45 mg/L, which was approximately 65-fold higher than that of the wild-type strain BY4741 and 229% higher than that in ordinary SD-His-Ura medium. It was the highest titer for friedelin production to date. Our work provides a good example for triterpenoid production in microbial cell factories and lays a solid foundation for the mining, pathway analysis, and efficient production of valuable triterpenoids with friedelin as the skeleton.

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Objective To evaluate the antimicrobial activity of the methanol extract from the stem bark of Drypetes tessmanniana, fractions (DTB1-5) as well as compounds [friedelin (2), 3,7-dioxofriedelane (3), 3,15-dioxofriedelane (4), 3beta- O-(E)-3,5-dihydroxycinnamoyl-11-oxo-olean-12-ene (6), and 3beta,6alpha-dihydroxylup-20(29)-ene (7). Methods Agar disc diffusion was used to determine the sensitivity of the above samples, whilst the microdilution method was used for the determination of the minimal inhibitory concentration (MIC) and the minimal microbicidal concentrations (MMC). Results The diffusion test showed that the crude extract was able to prevent the growth of all tested organisms. All other samples showed selective activity. The inhibitory effect of the fraction DTB2 was noted on 63.7%, that of DTB1 and DBT3 on 54.6%, whilst DTB4 and DTB5 were active on 9.1% of the 11 tested organisms. The tested compounds prevented the growth of 81.8% of the tested microbial species for compounds 3 and 4, 36.7% for compound 6, and 18.2% for compound 7. The results of the MIC determinations indicated perceptible values for DTB and compound 4 on 81.8% of the tested organisms. For other samples, MICs were detected on 0-63.7%. The lowest MIC value (78.12 microg/mL) for the crude extract and fractions (DTB2) was observed on M. audouinii. The corresponding value for isolated compounds (156.25 microg/mL) was noted with compounds 3 on S. faecalis and 4 on M. audouinii audouinii. The results of the MMC determination suggested that the microbicidal effect of most of the tested samples on the studied microorganisms could be expected. Conclusion The methanol extract from the stem bark of Drypetes. tessmanniana (Euphorbiaceae) as well as some of the isolated compounds might be potential sources of new antimicrobial drugs.

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The MeOH extract of the stem barks of Drypetes tessmanniana (Euphorbiaceae) afforded two new triterpene derivatives characterized as 3beta-O-(E)-3,5-dihydroxycinnamoyl-11-oxo-olean-12-ene and 3beta,6alpha-dihydroxylup-20(29)-ene together with seven known compounds. Their structures were established on the basis of spectral analysis.

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