| Summary: | Natural product studies explore potential and interesting new compounds to discover innovative drugs. <i>Nigella sativa</i> (<i>N. sativa)</i> (Ranunculaceae) is traditionally used to treat diabetes. Flavonoids and triterpenoid mostly show anti-diabetic activity. The current study aim to identify new compounds by a systematic study of the anti-oxidant and anti-diabetic activity of aerial parts of <i>N. sativa</i> concerning. Phytochemicals were isolated from the methanolic extract of aerial parts of the plant by column chromatography and identified by nuclear magnetic resonance spectroscopy and mass spectroscopy. A new triterpenoid saponin glycoside was isolated along with flavonoids. The anti-diabetic study was carried out by DPPH, ABTS, <inline-formula> <math display="inline"> <semantics> <mi mathvariant="sans-serif">α</mi> </semantics> </math> </inline-formula>-glucosidase, and protein tyrosine phosphatase 1B assays at doses of 12.5 to 250 µM. The isolated phytochemicals were identified as 3-O-(β-<span style="font-variant: small-caps;">d</span>-xylopyranosyl-(1-3)-α-<span style="font-variant: small-caps;">l</span>-rhamnopyrnaosyl-(1-2)-α-<span style="font-variant: small-caps;">l</span>-arabinopyranosyl]-28-O-(α-<span style="font-variant: small-caps;">l</span>-rhamno-pyranosyl-(1-4)-β-<span style="font-variant: small-caps;">d</span>-glucopyranosyl-(1-6)-β-<span style="font-variant: small-caps;">d</span>-glucopyranosyl] hederagenin (<b>1</b>), flaccidoside III (<b>2</b>), catechol (<b>3</b>), quercetin-3-gentiobiosides (<b>4</b>), magnoflorine (<b>5</b>), nigelflavonoside B (<b>6</b>), nigelloside (<b>7</b>), quercetin sphorotrioside (<b>8</b>), kaempferol-3, 7-diglucoside (<b>9</b>), kaempferol 3-O-rutinoside (<b>10</b>), rutin (<b>11</b>), 3-O-[α-<span style="font-variant: small-caps;">l</span>-rhamnopyranosyl-(1→2)-α-<span style="font-variant: small-caps;">l</span>-arabinopyranpsylhederagenin (<b>12</b>), 3β,23,28-trihydroxyolean-12-ene-3-O-α-<span style="font-variant: small-caps;">l</span>-arabinopyranoside(1→4)-a-rhamnopyranosyl,(1→4)-β-<span style="font-variant: small-caps;">d</span>-gluco-pyranoside (<b>13</b>), 3-O-α-<span style="font-variant: small-caps;">l</span>-rhamnopyranosyl-(1→2)-α-<span style="font-variant: small-caps;">l</span>-arabinopyranpsyl]-28-O-β-<span style="font-variant: small-caps;">d</span>-gluco-pyranosyl hederagenin (<b>14</b>), and α-hederin (<b>15</b>). These were isolated and are reported for the first time in this study. Compared <b>13</b> was identified as a new compound. Compound <b>2</b> was isolated for first time from the genus <i>Nigella</i>. Compound <b>6</b> was found to be the most active in the DPPH, and ABTS assays and compound <b>10</b> was found to be the most active in the α-glucosidase assay, with IC<sub>50</sub> 32.7 ± 0.1, 95.18 ± 0.9, 214.5 ± 0.0 µΜ, respectively. Compound <b>12</b>, at a dose of 125 µΜ, showed anti-diabetic activity in a PTP1B assay with IC<sub>50</sub> 91.30 <inline-formula> <math display="inline"> <semantics> <mrow> <mo>±</mo> </mrow> </semantics> </math> </inline-formula> 2.5 µΜ. In conclusion, the anti-diabetic activity of <i>N. sativa</i> is due to its flavonoids and TTSGs. Therefore, our studies suggest that the aerial parts of <i>N. sativa</i> are also a valuable and alternate source of valuable phytochemicals that could be used to develop anti-oxidant and anti-diabetic medicines.
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