Oxalic acid is present in tomatoes, spinach, and especially in carambola and rhubarb; rhubarb leaves and unripe carambolas are toxic because of high concentrations of oxalic acid.
ɑːksˈælɪk ˈæsɪd ɪz pɹˈɛzənt ɪn təmˈeɪɾoʊz, spˈɪnɪtʃ, ænd ɪspˈɛʃəli ɪn kˌæɹɐmbˈoʊlə ænd ɹˈuːbɑːɹb; ɹˈuːbɑːɹb lˈiːvz ænd ʌnɹˈaɪp kˌæɹɐmbˈoʊləz ɑːɹ tˈɑːksɪk bɪkˈʌz ʌv hˈaɪ kˌɑːnsəntɹˈeɪʃənz ʌv ɑːksˈælɪk ˈæsɪd.