**5. Conclusions**

Red yeas<sup>t</sup> rice is a well-known material which has been widely used for decades, but the chemistry and bioactivity of the constituents are still not so clear. Previous investigation of *Monascus* species had isolated different skeleton constituents, mainly azaphilones and monacolin analogs. However, some minor compounds such as benzenoid derivatives or other types of compounds from *Monascus* species have received less attention. Accordingly, it is still worth investigating the ingredients and bioactivity of red yeas<sup>t</sup> rice.

In this report, we committed to explore unusual skeleton compounds in *M. purpureus* wmd2424, and successfully found new xanthonoid, cyclohexenone, γ-lactone, isoquinoline, and azaphilone skeleton compounds. Xanthonoids are yellow pigments in a C6-C1-C6 system and restricted in a few families of higher plants, some fungi and lichens, and has seldom been found in *Monascus* spp. [46] This is the second report of isolating xanthonoids from *Monascus spp*, which represent different yellow azaphilone pigments (monascin, ankaflavin) from this genus. The structures of these isolates were determined using spectroscopic experiments. The BuOH soluble fraction from the *M. purpureus* wmd2424 fermentation broth was tested for antifungal activities. Our results indicated that compounds **3**–**5** displayed moderate antifungal activities against *Aspergillus niger*, *Penicillium italicum*, *Candida albicans*, and *Saccharomyces cerevisiae*. It is worth mentioning that the chemical composition of *M. purpureus* wmd2424 has never been studied. The result indicated *M. purpureus* wmd2424 could produce more metabolites with extensive antifungal activity, and that its metabolites in other mediums were worth being studied further.

**Author Contributions:** M.-J.C. designed the research and performed the research; M.-D.W. conducted the biological assays; M.-J.C. and J.-J.C. performed the isolation and structure elucidation of the constituents; and M.-J.C. organized the data and wrote the paper. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was kindly supported by the Ministry of Science and Technology, R.O.C. (MOST-108-2320-B-080-002-, MOST-109-2622-E-080-001-, and MOST-110-2320-B-080-001-).

**Acknowledgments:** The authors thank Senior Researcher Min Tseng for her help in strain identification, cultivation, and fermentation, and thank Senior Technician Chyi Jia Wang of the Center for Resources, Research, and Development (CRRD) at Kaohsiung Medical University for measuring the 2D NMR data.

**Conflicts of Interest:** The authors declare no conflict of interest.
