Newly described antioxidant disecolactonic ergosteroids from marine cuttlefish Sepia pharaonis: Pharaonoids A-B as prospective carbohydrate digestive enzyme inhibitors.

Biochemical investigation of crude solvent extract of pharaoh cuttlefish Sepia pharaonis (family Sepiidae) led to the isolation of two undescribed disecolactonic ergosteroids, pharaonoids A-B. The compounds were characterized as 11β-acteoxy-7α-hydroxy-19-Nor-1,10:9,10-disecoergosta-3-ene-6 ¹ -oxa-1-one (pharaonoid A) and 11β-hydroxy-19-Nor-1,10:9,10-disecoergosta-3-ene-6 ¹ -oxa-1-one (pharaonoid B) in conjunction with spectroscopic analysis encompassing one and two-dimensional nuclear magnetic resonance and mass spectrometric analyses. Pharaonoid A, bearing an acetoxy and hydroxyl groups, respectively at C-11 and C-7 positions exhibited considerably greater inhibition potential against carbohydrate hydrolysing enzymes α-amylase (IC ₅₀ 1.14 mM) and α-glucosidase (IC ₅₀ 1.23 mM) than those displayed by pharaonoid B (IC ₅₀ 1.49/1.38 mM), and was proportionate with those exhibited by standard drug acarbose (IC ₅₀ 0.60 and 0.40 mM, respectively), thereby recognizing the anti-hyperglycemic potential of pharaonoid A. Promising anti-oxidant property for pharaonoid A (IC ₅₀  ∼ 1 mM) could conceivably corroborate its attenuation potential against carbohydrate digestive enzymes. Greater electronic parameters along with optimum lipophilic-hydrophobic balance of pharaonoid A were directly corroborated to the anti-carbolytic properties occurring via transcellular mechanism. Greater binding energies (-9.50 kcal mol ^-1 ) and inhibition constant (Ki 48.21 nM) at the active site of α-amylase enzyme were displayed by pharaonoid A than those exhibited by its B analogue. Promising bioactive properties of the disecolactonic steroids isolated from the marine pharaoh cuttlefish are anticipated to be utilized as functional food components and potential nutraceuticals against oxidative stress and hyperglycemic disorders.
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