Abstract: A cis- or trans-stilbenoid of the general formula (1): in which each of R1, R2, R3, R4 and R5 is hydrogen or hydroxy, or a glycosylated or oligomeric form thereof, is produced by cultivating a micro-organism producing said stilbenoid, in a multi-phase system comprising at least an aqueous first phase containing said micro-organism and a second phase immiscible with said aqueous phase in which (e.g. as which) said stilbenoid accumulates. The second phase may be said stilbenoid or a free or encapsulated solvent compatible with the growth of the micro-organism, for instance an ester.