Catalyzes the iterative condensations of 5 molecules of malonyl-CoA to produce a pentaketide 5,7-dihydroxy-2-methylchromone. 4 H(+) + 5 malonyl-CoA = 5,7-dihydroxy-2-methyl-4H-chromen-4-one + 5 CO2 + 5 CoA + H2O kcat is 0.445 min(-1). Optimum pH is 6.0-8.0. Secondary metabolite biosynthesis; flavonoid biosynthesis. Homodimer. A.arborescens is a medicinal plant rich in aromatic polyketides, such as pharmaceutically important aloenin (hexaketide), aloesin (heptaketide) and barbaloin (octaketide). Belongs to the thiolase-like superfamily. Chalcone/stilbene synthases family.