From Leaf to Line: A Quantitative Study of Spinach (Spinacia oleracea l.) Extract as Paper Highlighter

Spinach (Spinacia oleracea L.) contains natural chlorophyll pigments that can be utilized as an environmentally friendly dye for paper-based applications. Due to concerns about the environmental impact of synthetic fluorescent dyes and potential health risks associated with petroleum-based stationery products, plant-based extracts are being explored as sustainable alternatives for highlighter ink production. This study investigated the effectiveness of spinach extract as a natural paper highlighter by examining five dependent variables: color visibility measured through CIE Lab colorimetric analysis, color retention over 1, 2, 3, and 24 hours under ambient conditions, smear resistance using a five-point rating scale, color stability under exposure to seven visible light wavelengths (ROYGBIV), and production cost efficiency. The independent variable consisted of five formulations with varying spinach masses (50 g, 150 g, and 250 g) and acid concentrations (1.5 g and 3 g each of citric and ascorbic acid) as stabilizing agents. The study employed a true experimental quantitative design using a Pretest–Posttest Control Group Design conducted at the Maguikay National High School Science Laboratory, where spinach extract highlighters were compared with a commercial synthetic highlighter as the control group. One-way ANOVA revealed significant differences among formulations in color visibility and color retention. Formulation E (250 g spinach with 1.5 g each of citric and ascorbic acid) demonstrated the most balanced performance, achieving visibility comparable to the commercial highlighter, high color retention, strong smear resistance, good light stability, and the lowest production cost (₱21.00 per unit), indicating that spinach extract highlighters represent a viable, sustainable, and cost-efficient alternative to synthetic paper highlighters.