Treatment with metal–organic frameworks (MOFs) elicits secondary metabolite accumulation in Aquilaria crassna (agarwood) callus culture

Abstract Thymelaceaous trees are prized for accumulating fragrant resins composed of hundreds of secondary metabolites in their woody tissues. Slow growth and increasing consumer demand have stretched natural sources of agarwood trees to being endangered and alternative production modes, including silviculture and tissue culture, are currently being investigated. Dedifferentiated tissue culture of agarwood trees provides a means of cell propagation independent of environmental context. However, secondary metabolite accumulation, as found in fragrant resins, occurs largely in response to wounding. Here, we investigated the application of metal-organic frameworks (MOFs) as potential elicitors of secondary metabolite formation in Aquilaria crassna tissue culture. Callus cultures were exposed to five commercially available MOFs (UiO-67, MOF-808, HKUST-1, ZIF-67, and MOF-74) and ethanol extracts were analysed using GC-MS to quantify secondary metabolite accumulation in MOF-exposed cultures compared to untreated cultures. Samples that were exposed to either of the two Zr-based MOFs exhibited metabolite production profiles that were similar to each other, (trans-2-Carboxy-cyclo-hexyl)-acetic acid was reduced in the presence of all MOFs, the Cu-containing HKUST-1 MOF increased palmitic acid levels, and ZIF-67 (at 20 mg/L) was found to elicit the highest accumulation of secondary metabolites with potential fragrance applications. These results demonstrate the possibility of eliciting secondary metabolites from dedifferentiated agarwood tree cell culture and may provide an alternative means of sourcing fragrant specialty chemicals from these plants.