Figure 1: Structures of pyridoxine derivatives used in this study: 1: 3,3,5-trimethyl-8,8-dioctyl-1,7,8,9-tetrahydro-dioxino-d]pyrrolo-b]pyridin-8-ium chloride; 2: N,N′-((2,2,8-trimethyl-4H-dioxino-c]pyridine-5,6-diyl)bis(methylene))bis(N,N-dimethyloctan-1-aminium) dichloride; 3: N,N-dimethyl-N-((2,2,8-trimethyl-4H-dioxino[4,5-c]pyridin-5-yl)methyl)octadecan-1-aminium chloride; 4: 5,6-bis(triphenylphosphonio(methyl))-2,2,8-trimethyl-4H-dioxino-c]pyridine dichloride; 5: 5,6-bis[(tributylphosphonio)methyl]-2,2,8-trimethyl-4H-dioxino-c]pyridine dichloride; 6: 5,6-bis[triphenylphosphonio(methyl)]-8-methyl-2-propyl-4H-dioxino-c]pyridine dichloride.