This is what I’ve found:
Apparently Plantain or Ribwort contains: vitamins A, B, C and K, Calcium, Iron, Silica, Phosphorus, Magnesium, Selenium, Sodium, Zinc, Potassium and Sulphur.
Medicinal uses: Laxative, Astringent, Diuretic, Expectorant, Hemostatic, Antiseptic, Antispasmodic, Stomachic, Tonic, Antitussive, Vulnerary, Digestive.
Non-medical uses of ribwort plantain: Leaves can be eaten raw or cooked (Not really very nice) The very young leaves are supposed to be somewhat better and are less fibrous. Seed - cooked. Used like sago. The seed can be ground into a powder and added to flours when making bread, cakes or whatever.