Wang, S.; Yu, Z.; Wang, C.; Wu, C.; Guo, P.; Wei, J. Chemical Constituents and Pharmacological Activity of Agarwood and Aquilaria Plants. Molecules 2018, 23, 342. [ Google Scholar] [ CrossRef] [ PubMed][ Green Version] Aquilaria belongs to the Thymelaeaceae family of angiosperms, which is endemic to the Indomalayan realm. To date, there is a total of 21 Aquilaria species which have been documented and 13 of them are recognized as the agarwood-producing species ( Lee and Mohamed, 2016). The destructive exploitation of agarwood, however, has badly affected the wild population of all Aquilaria species. As a consequence, the genus is now listed as endangered species and protected under Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) regulation due to a drastic declination of the species in the wild (Convention On International Trade In Endangered Species [CITES], 2004; Lee and Mohamed, 2016). High demand of quality agarwood in conjunction with the depletion of the wild Aquilaria trees implied that the price of the agarwood will continue to soar. As an alternative, mass cultivation and large plantation of Aquilaria trees which serve as a sustainable source to obtain agarwood have greatly resolved the shortage of agarwood supply in the global market. Ruggeri, M.; Coretti, S.; Prete, S.; Romano, F.; Orlando, V.; Codella, P.; Di Brino, E. Economic evaluation of screening programs for hepatitis C virus infection: Evidence from literature. Risk Manag. Health Policy 2015, 8, 45–54. [ Google Scholar] [ CrossRef] [ PubMed][ Green Version] Santini, A.; Tenore, G.C.; Novellino, E. Nutraceuticals: A paradigm of proactive medicine. Eur. J. Pharm. Sci. 2017, 96, 53–61. [ Google Scholar] [ CrossRef] Kulshrestha, A.; Rupanwal, R.; Singh, N.; Panhekar, D.; Ey, J. Therapeutic Potential of Chromones. Int. J. Chem. Sci. 2017, 15, 200. [ Google Scholar]

Vanguru, M.; Merugu, R.; Garimella, S.; E, L. A Review on the Synthetic Methodologies of Chromones. Asian J. Pharm. Clin. Res. 2018, 11, 9–16. [ Google Scholar] [ CrossRef] Mei, W.L.; Lin, F.; Zuo, W.J.; Wang, H.; Dai, H.F. Cucurbitacins from fruits of Aquilaria sinensis. Chin. J. Nat. Med. 2012, 10, 234–237. [ Google Scholar] [ CrossRef] Pateraki, I.; Heskes, A.M.; Hamberger, B. Cytochromes P450 for Terpene Functionalisation and Metabolic Engineering. Adv. Biochem. Engi./Biotechnol. 2015, 148, 107–139. [ Google Scholar] [ CrossRef] Li, W.; Liao, G.; Dong, W.-H.; Kong, F.-D.; Wang, P.; Wang, H.; Mei, W.-L.; Dai, H.-F. Sesquiterpenoids from Chinese Agarwood Induced by Artificial Holing. Molecules 2016, 21, 274. [ Google Scholar] [ CrossRef] Proença, C.; Albuquerque, H.M.T.; Ribeiro, D.; Freitas, M.; Santos, C.M.M.; Silva, A.M.S.; Fernandes, E. Novel chromone and xanthone derivatives: Synthesis and ROS/RNS scavenging activities. Eur. J. Med. Chem. 2016, 115, 381–392. [ Google Scholar] [ CrossRef]Zhang, Z.; Han, X.M.; Wei, J.H.; Xue, J.; Yang, Y.; Liang, L.; Li, X.J.; Guo, Q.M.; Xu, Y.H.; Gao, Z.H. Compositions and antifungal activities of essential oils from agarwood of Aquilaria sinensis (Lour.) Gilg induced by Lasiodiplodia theobromae (Pat.) Griffon. Maubl. J. Braz. Chem. Soc. 2014, 25, 20–26. [ Google Scholar] Nakanishi, T.; Yamagata, E.; Yoneda, K.J. Jinkoh-eremol and jinkohol II, two new sesquiterpene alcohols from agarwood. Chem. Soc. Perkin Trans. 1983, 1, 601–604. [ Google Scholar] [ CrossRef]

Dai, H.F.; Liu, J.; Han, Z.; Zeng, Y.B.; Wang, H.; Mei, W.L. Two new 2-(2-phenylethyl) chromones from Chinese aglewood. J. Asian Nat. Prod. Res. 2010, 12, 134–137. [ Google Scholar] [ CrossRef] [ PubMed] Demetgül, C.; Beyazit, N. Synthesis, characterization and antioxidant activity of chitosan-chromone derivatives. Carbohydr. Polym. 2018, 181, 812–817. [ Google Scholar] [ CrossRef] [ PubMed] Adhikari, S.R.; Pokhrel, K.; Baral, S.D. Economic Value of Agarwood and Its Prospects of Cultivation. Int. J. Appl. Sci. Biotechnol. 2021, 9, 23–31. [ Google Scholar] [ CrossRef] Gao, H.-Y.; Wang, H.-Y.; Li, G.-Y.; Du, X.-W.; Zhang, X.-T.; Han, Y.; Huang, J.; Li, X.-X.; Wang, J.-H. Constituents from Zhuyeqing Liquor and their inhibitory effects on nitric oxide production. Phytochem. Lett. 2013, 7, 150–155. [ Google Scholar] [ CrossRef] Tawfik, H.A.; Ewies, E.F.; El-Hamouly, W.S. ChemInform Abstract: Synthesis of Chromones and Their Applications during the Last Ten Years. ChemInform 2015, 46. [ Google Scholar] [ CrossRef]Chhipa, H.; Kaushik, N. Fungal and Bacterial Diversity Isolated from Aquilaria malaccensis Tree and Soil, Induces Agarospirol Formation within 3 Months after Artificial Infection. Front. Microbiol. 2017, 8, 1286. [ Google Scholar] [ CrossRef] [ PubMed] Nazhand, A.; Durazzo, A.; Lucarini, M.; Romano, R.; Mobilia, M.A.; Izzo, A.A.; Santini, A. Human health-related properties of chromones: An overview. Nat. Prod. Res. 2019, 34, 137–152. [ Google Scholar] [ CrossRef] Liao, G.; Dong, W.-H.; Yang, J.-L.; Li, W.; Wang, J.; Mei, W.-L.; Dai, H.-F. Monitoring the Chemical Profile in Agarwood Formation within One Year and Speculating on the Biosynthesis of 2-(2-Phenylethyl)Chromones. Molecules 2018, 23, 1261. [ Google Scholar] [ CrossRef][ Green Version]

Rohmer, M. The discovery of a mevalonate-independent pathway for isoprenoid biosynthesis in bacteria, algae and higher plants†. Nat. Prod. Rep. 1999, 16, 565–574. [ Google Scholar] [ CrossRef]Li, W.; Mei, W.L.; Dong, W.H.; Cai, C.H.; Gai, C.J.; Dai, H.F. Study on chemical constituents of Chinese agarwood “Qi-Nan”. J. Trop. Subtrop. Bot. 2019, 27, 196–202. [ Google Scholar] Overharvesting and habitat loss threatens some populations of agarwood-producing species. Concern over the impact of the global demand for agarwood has thus led to the inclusion of the main taxa on CITES Appendix II, which requires that international trade in agarwood be monitored. Monitoring is conducted by Cambridge-based TRAFFIC (a joint WWF and IUCN programme). [40] CITES also provides that international trade in agarwood be subject to controls designed to ensure that harvest and exports are not to the detriment of the survival of the species in the wild. [41]