Garcioblons A–F, Polycyclic Polyprenylated Acylphloroglucinols with Diverse Rearranged Skeletons from Garcinia oblongifolia

Garcioblons A-F (1-6), six unprecedented polycyclic polyprenylated acylphloroglucinols (PPAPs) formed via intramolecular Diels-Alder (IMDA) reactions from monocyclic polyprenylated acylphloroglucinols (MPAPs), were isolated from Garcinia oblongifolia. Their structures were elucidated through spectroscopic analysis and quantum calculations. Structurally, compound 1 is the first PPAP characterized by an unprecedented 6/6/5/7/6/5/6/5 octacyclic ring system with a 11-oxatetracyclo[8.5.1.01,12.05,10]hexadecane motif, while 2-4 are its biogenetically related analogues. Compound 5 possesses a caged 6-oxatetracyclo[7.3.1.12,10.02,7]tetradecane new carbon skeleton, while compound 6 features a 4-oxatricyclo[7.4.0.01,5]tridecane structure. Additionally, compound 1 demonstrated notable antitumor activities by inhibiting autophagic flux and stimulating oxidative stress, which collectively resulted in reduced cell proliferation and induced apoptosis.