Diosgenin and solasodine-based saponins and sapogenines—Effects of structural modifications on Panagrellus redivivus, Spodoptera littoralis and Trichoderma reesei

• Diosgenin- and solasodine-based saponins are plant secondary metabolites. • Modification of sapo(ge)nins via glycosylation and ring-opening led to new compounds. • Investigation of structure–activity-relationship via bioassays with 3 model organisms. • Glycosylation increased nematode mortality but elevated feeding rate of herbivores. • Solasodine and its derivatives showed high antifungal activity. Saponins are a large class of plant natural products that exhibit a great variety of biological and pharmacological properties. Starting from diosgenin and solasodine nine derivatives were synthesized. Via Koenigs-Knorr synthesis glucose was attached to diosgenin and solasodine, respectively. Furthermore, glucose, cellobiose and glucuronic acid methyl ester were used as trichloroacetimidates in glycosylation reactions with diosgenin. Additionally, via reductive ring-opening reaction the F-ring of diosgenin as well as solasodine was modified, resulting in two compounds, 26-amino-(22 R ,25 R /25 S )-furost-5-en-3β-ol. The same reaction was applied to (22 R ,25 R )-spirost-5-en-3β-yl α- d -3′,4′,6′-tri- O -acetyl-glucopyranoside and (22 R ,25 R )-spirost-5-en-3β-yl β- d -2′,3′,6′-tri- O -acetyl-glucopyranosyl-(1 → 4)-β- d -8′,9′,10′,12′-tetra- O -acetyl-glucopyranoside, leading to new compounds. Biological activities of selected compounds as well as isoflavone glycosides were tested on Panagrellus redivivus L., Spodoptera littoralis Boisduval and Trichoderma reesei QM6a. We show that the bioactivity is highly variable, depending not only on the tested organisms, but also on the glycosylation pattern. Especially 26-amino-(22 R ,25 R )-furost-5-en-3β-ol exhibited high nematocidal (75 % mortality rate), anti-herbivorous (feeding rate reduced to 0.4 % leaf area/min) as well as anti-fungal properties (47 % increased anti-fungal activity compared to solasodine) whilst the other tested compounds exhibited only moderate activities.