Metal complexes of macrocycles and/or isoprenoids and/or linear tetrapyrroles by mechanochemistry (grinding or milling), preparation method thereof, sunscreen/concealer/UV absorber thereof, self-assembled coating material thereof, superamphiphilic material or surfaces thereof, hair dyeing thereof and other uses thereof. Converting biomass, including products from its own process-line wastes, into high value products such as biofuel, bioplastics and biochemicals in an attempt to replace oil consumption has become nowadays a challenge for innovation. In one embodiment of the present invention, a novel product obtained from the solvent-free mechanochemical reaction (grinding and milling) of biomass and a metal alkoxide is produced. In one embodiment of the present invention, Spirulina biomass, comprising macrocycles (chlorophyll) and isoprenoids (P-carotene) and linear tetrapyrroles (phycobilins attached to proteins), is ground or milled together with a metal alkoxide to produce a stable colored material.