Microwave hydrodiffusion and gravity was performed in a Milestone
EOS-G microwave laboratory oven (Sorisole Bergamo, Italy)
consisting in a multimode microwave reactor operating with a
frequency of 2.45 GHz and variable power (10Wincrements, maximal
value: 900 W). The extraction vessels are made of Pyrex and
have a capacity of 1 L. During extraction, temperature was continuously
monitored and recorded by sensors made of optic fibres
inserted both in the plant material and in the reactor. The press
cake was heated for 20 min at atmospheric pressure and at a
constant power density of 1W/g without addition of solvent. The
direct interaction of microwaves with plant water triggers the release
of plant cell contents and the corresponding extract moves
downwards under the effect of earth gravity through a spiral condenser
outside the microwave cavity. The extraction was continued
until no more extract was collected or overheating was
detected.