neohesperidin

The bitter flavanone glycoside neohesperidin in bitter orange (C. aurantium) leaves, flower buds, and fruit consistently exceeds the levels of the paired bitter glycoside naringin, as confirmed by HPLC quantitation (fruit ratio: 1.02–3.15). However, developmental concentration trajectories differ by organ: in leaves the neohesperidin/naringin ratio decreases monotonically from 8.83 to 5.18, whereas in flower buds and fruit the progression is non-monotonic, following a bell-shaped curve rather than steady decline.

In flower buds, the ratio peaks above 3 during early development (buds 1–10 days before flowering), then decreases to approximately 2 during the differentiation stage, reaching its lowest point of 1.61 just before flowering, before recovering to approximately 2 after flowering—a non-monotonic progression. Fruit similarly exhibits this pattern: the ratio peaks at 3.15 when the fruit is 3–7 mm in diameter, then drops rapidly to 1.13 at 35 mm diameter, and continues falling to 1.02 at maturity (61 mm diameter, approximately 200 days after flowering). Both organs are characterized by a bell-shaped concentration curve rather than steady decline.

The same 1992 study dissected 30-day-old flower buds into 6 parts (receptacle, ovary, stigma, petal, filament, anther) and found the neohesperidin/naringin ratio varies widely by part, ranging from 0.98 (receptacle) to 3.83 (stigma). The ovary and stigma show the highest concentrations; the receptacle, petal, and filament show low concentrations. However, because petals comprise 42.34% of total flower weight, their contribution is not negligible despite their low ratio. This organ-level breakdown complements the aggregate bud-level transition data.

The concentration decline during development is explained by the authors as due to 『細胞成長によるフラボノイドの希釈』 (in translation: "flavonoid dilution by cell growth"). The concentration reaches its maximum during the logarithmic expansion phase of organ development, but as cell volume increase outpaces compound accumulation, the concentration (as a ratio) declines, while total content per organ is described as continuing to increase over the same period. This dilution pattern is also reported for naringin and is not unique to neohesperidin alone.

A comprehensive analysis of fruit juice from multiple Citrus genotypes and Citrus × Poncirus trifoliata hybrids found that neohesperidin content correlated positively with bitterness scores from trained sensory panelists (r = 0.46). Among known bitter compounds, this correlation strength ranks below limonin (r = 0.57) and apigenin (r = 0.52) but is comparable to naringin (r = 0.46) and poncirin (r = 0.46). Neohesperidin, poncirin, and naringin were present only in the pomelo cultivar 'Melogold' among the samples analyzed.