In some embodiments, the present invention relates to an enrichment process that involves a separation and/or fractionation and/or enrichment of monounsaturated fatty acid/ester molecules from polyunsaturated fatty acid/ester molecules or, correspondingly, monounsaturated molecules from saturated molecules. Such processes are at least partially based on π(pi)-complexation between metal ions and unsaturated bonds of the extractible molecules (fatty acids/esters), wherein a greater degree of unsaturation provides for greater coordinating (bond) strength and corresponding selectivity in the associated π-complexation with metal ions.