The present invention refers to compounds of the general formulae Ia to Ie as defined above for use as/in a composition (especially foods and dietary supplements, cosmetic, as well as pharmaceutical compositions) for the prevention and improvement of muscular disorders and for the improvement of muscle function. Other fields of use are disorders connected to impaired lipid metabolism, impaired glucose metabolism and impaired insulin action, obesity, overweight conditions, eating disorders such as bulimia and anorexia nervosa, cardiovascular diseases, atherosclerosis, vascular diseases, heart failure, inflammatory disorders such as arthritis, rheumatoid arthritis, osteoarthritis, gout, gastrointestinal disorders such as inflammatory bowel syndrome, Crohn's disease, gastritis, irritable bowel syndrome and ulcerative colitis, skin related conditions such as psoriasis, eczema, burns, dermatitis, and allergy, respiratory disorders such as asthma, chronic obstructive pulmonary disease (COPD), allergic diseases, and/or bone disorders such as osteoporosis and osteopenia. The compounds may also be used for bodyshaping, for improving the muscle:fat ratio or for accelerating skin wound healing. The present invention is also directed to dietary compositions such as (fortified) food, beverages, (fortified) feed, food additives, beverage additives, feed additives, clinical nutrition, dietary supplements, functional food, functional feed and nutraceuticals and to pharmaceutical compositions containing such compounds, to methods of treating the above mentioned disorders/diseases in mammals including humans and to the compounds of the formula I themselves. Another object of the present invention is the use of such compounds for the manufacture of a composition for the treatment of such disorders/diseases as mentioned above.