Catalyzes the conversion of alpha-humulene to 10-hydroxy-alpha-humulene in the second step of zerumbone biosynthesis, a predominating potential multi-anticancer agent. alpha-humulene + O2 + reduced [NADPH--hemoprotein reductase] = 10-hydroxy-alpha-humulene + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Expressed at highest level in rhizomes and much less in leaves. Not expressed in stems. The recommended numbering of humulene gives 10-hydroxy-alpha-humulene as the product rather than 8-hydroxy-alpha-humulene as used by the literature. Belongs to the cytochrome P450 family.